A serious study of the application of PPP in the field of social security is an important proposition related to major political tasks such as helping to fully realize social fairness and justice，building a well-off society in an all-round way and poverty alleviation.

Through the comparative study between social security PPP projects and other PPP projects，this paper summarizes the six basic attributes of social security PPP projects，such as mandatory by law，extensive sociality，strong public welfare，specificity of protected groups，adaptability to the social development，and distinct politics nature. The application of social security PPP projects must conform to and meet the basic attributes of security PPP projects.

Therefore，combined with the practice of social security PPP projects，the author summarizes eleven application characteristics and five problems that should be paid attention to in the implementation. The author’s research on the theoretical attributes of social security PPP projects and the summary of practical experience have important theoretical and practical significance for the comprehensive understanding and control of the essential characteristics of social security PPP projects，and the innovative and flexible implementation of PPP projects.