【摘要】This issue of Population and Development Forum focuses on population security in China. Major questions to be addressed are: What is population security? How to measure and quantify population security? What are the international perspectives? What are the challenges associated with population security in China? In a historical perspective, population security thinking involves a development process with changing population problems. Population security in China is characterized by complexity, diversity, and dynamicity. Population security, involving population quantity and quality, structure and their relations to resources and environment, is crucial to China’s development. The changing notion from “population problem” to “population security” is of both theoretical and practical significance, addressing population and development in a comprehensive, harmonious and globalized approach.