Based on the attribute of the public pension insurance system,this paper analyzes the structure of the public pension insurance system during the planned economy period and the transition period from a planned economy to a market economy in China,and based on this,re-position the public pension insurance system on modern sense.This paper advocates that the existing basic old-age insurance systems in enterprises being integrated can be as the public pension insurance system model on modern sense.It changes "social pooling and individual accounts combined" into "social pooling and individual accounts of the portfolio",thus the basic old-age insurance system is separated into two mutually independent but interrelated "social pension insurance system" and "endowment insurance system for individual accounts",the public pension insurance system,that is,consists of co-coordinating social pension insurance system and individual accounts of the endowment insurance system.