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.