In recent years， the supply and demandconflictof pension service has emerged as a serious problem as the ageing of the population is getting increasingly severer in China. The government has issued a series of policy documents relating to the social pension service， and Beijing， Shanghai and other megacities have set the objectives to establish the “9064” and “9073” social pension service system and put these systems in practice in depth. In June 2017， the State Council issued the “Opinions on Formulating and Implementing the Aged Care Service Project”. The document further acknowledges and highlights the fundamental position of the family-based care service for the old in China's pension service. It accords with the concrete requirement of“establishing a social pension service system with the family as the base， the community as the reliance and the institution as the support”specified inthe “Law of the People's Republic of China on Protection of Rights and Interests of the Elderly People”， and interprets the national pension service policy in the new time. To respond to the upcoming arrival of a society with deep ageing and accelerate the construction of the social pension service system， this report will analyze the status quo of population ageing and the reason for the construction of the social pension service system， and streamline the internal contact between the PPP mode and the social pension service. At the same time， this report takesthe social pension service system of Shichahai Sub-district of Xicheng District for example to identify problems in the system and propose corresponding suggestions.