Abstract: The paper reviews the background and historical process of China's basic national policy of family planning，analyses the new situation and new features of China's population and development，and summarizes the strategic tasks and safeguard mechanisms of maintaining the long-term balanced development
of China's population． China now allows couples to have a second child if either parent is an only child． The paper also introduces the significance and the progress of the policy relaxation． China's family planning over the last 40 years has helped create the external balanced development of population with economy，society，resources and environment． However，problems concerning quantity，quality，structure and distribution of population will crop up in the first half of this century． The external and internal balanced development of China's population in the second half of this century largely depends on the current and future fertility level，calling for scientific and appropriate policy making． As the objective of China's population development is turning from cubing population growth into promoting long-term balanced development of population，China's family planning programme must keep up with the new trend and adopt a new model．

Keywords: Basic National Policy of Family Planning, Long-term Balanced Development of Population, Adjustment and Improvement of Fertility Policy, Two-child Policy for Couples if either Parent is an Only Child

摘要： 文章阐述我国实行计划生育基本国策的时代背景和历史进程，分析人口发展面临的新形势、新特点，概括了促进人口长期均衡发展的战略任务和保障措施，介绍调整完善生育政策的重要意义、总体思路及进展情况。文章指出，40多年的计划生育实践，推动了人口转变的提前到来，促进了经济发展和社会转型，为资源、环境的可持续发展创造了条件，形成了人口系统外部均衡发展的趋势。但是，人口系统内部的各类问题逐渐积累，将在本世纪中叶以前集中爆发。本世纪中叶以后，中国人口发展能不能实现内部和外部均衡，取决于目前和今后的生育水平，需要现在就作出正确的决策和引导。当前，我国人口发展的目标已经由控制人口增长为主转向促进人口长期均衡发展。计划生育工作必须顺应新的形势，转型发展。

关键词: 计划生育基本国策, 人口长期均衡发展, 调整完善生育政策, 单独二孩政策