Social construction is an important part of China's socialist cause, and the construction of social organizations is an important aspect of social construction. After the reform and opening up, as the third sector of non-governmental and non-profit organizations in social organizations, it plays an irreplaceable role in making up for government and market failure, providing public goods and services, relieving employment pressure, and improving citizens' moral cultivation. This paper first expounds the concept of the third sector, explains the necessity of the emergence and development of the third sector after China's reform and opening up, discusses the current development of the third sector in China, and makes a brief analysis of the problems arising from it, and puts forward some solutions for reference. Finally, it emphasizes the importance of the development of the third sector for social construction.