With a global perspective，drawing upon data related to population policy as well as the reproductive health/family planning published by the United Nations，this article examines the general trend and characteristics of population regulations and policy intervention across the world，and discusses the implications for the future reform of China’s family planning policy．We find that，in the past 30 years，regarding population policies in the fields of population growth，fertility level，aging，reproductive health/family planning as well as internal rural-urban migration，the number and proportion of countries with no population intervention in the world have considerably decreased．Such intervention has become a major world trend．More than 90% of the world’s countries or regions are currently practicing family planning，showing the universality，inclusiveness and strong vitality of this policy．The promotion of reproductive health has greatly enriched and expanded the traditional family planning practice．This article suggests that China’s family planning policy should promote reform and innovation in distinguishing basic concepts of population policy，integrating services，supporting external policies and bringing into full play the role of social organizations．

In conducting a more extensive and in-depth analysis of the new two-child policy, this article summarizes the results from the existing studies, and provides new interpretations and rethinking of the new family planning policy by looking at China’s fertility level with lifetime and regional perspective. Research shows that women’s lifetime fertility level is not as low as the period fertility level, and China has not fallen into the “low fertility trap”. A fundamental feature of China’s fertility pattern is the large regional differences. Adjustment of fertility policy needs an overall consideration. It is too early to suggest that the new fertility policy has had effects that are far below expectations when the policy has just been implemented for one year. The new fertility policy is transitional, and plays a role of reducing birth accumulation when moving to a universal two-child policy. Policy adjustment and change will bring about a full range of social impacts.

Based on a brief analysis of the narrowly-defined demographic transition and the classical model,this paper argues that the proposed theory of the second demographic transition broadly interprets the internal motivation and mechanism of action of the demographic changes by drawing upon the demographic "intermediate variables",reflecting on the relationship between modern demographic transition and social changes at the macro,meso and micro levels.Demographic transition is a multi-dimensional dynamic historical process,involving a set of transitions on marriage,reproduction,family,health,population control etc.Demographic transition is not only demographic change,but more importantly,is its nested social change.The unprecedented close relationship between the two reflects the social changes and social needs.Over the past 30 years China has made its population be adapted to economic development through family planning.In the next 30 to 50 years or even longer,China should make economic and social development be adapted to the changes and needs of the population.The end of development is to improve population survival and enhance life quality.

Using data of international and national fertility surveys,this paper analyzes the characteristics and changing trends of average birth intervals between the first and second child in different countries and periods with a focus on Chinese women in recent decades.Analytical results indicate that there are some common traits of birth intervals between the first and second child of women in different societies,and a two-year interval is the lowest limit of average "natural birth intervals." It’s necessary to execute restricted regulations of birth intervals between the first and second child in former fertility policies,and it has already achieved great effect.However,with the change of people’s fertility desire and voluntarily delay of the second birth,it is increasingly difficult to intervene in birth intervals by fertility policy,and it will provide good opportunities and conditions for government to adjust and improve relevant fertility policy.

Reviewing the changes in nuptiality and fertility behavior,family structure,and cause of death pattern of the Chinese population over recent decades,the author argues that it is far from complete and difficult to meet the practical demand of our era and population development to have an understanding demographic transition,especially the Chinese demographic transition from merely the conventional basic population dynamic involving birth,death and natural increase. Demographic transition is a multidimensional,dynamic and historical process,involving a combination of a serious of specific demographic transitions. Changes in birth rate,death rate and natural increase rate are only the surface or the "crust" of demographic transition.The "core" of demographic transition is the population behavior and its dynamic mechanism which are held by institutions,culture,and technology.Changes resulting from the "core" represent the intrinsic demographic transition.It is the important perspective and basis to understand the demographic transition with Chinese characteristics by looking at intrinsic demographic transition.Exploring the nature of demographic transition and reviewing the typical studies in demographic transition theory in China,the paper discusses future directions and research innovations in demographic transition theory.