In order to cope with population aging, the mutual pension mode of " time savings” has begun to pilot in some small communities. The purpose of this paper is to demonstrate the mechanism of introducing government-guaranteed community currency to mutual pension time savings under the background of population aging. Based on Samuelson-Diamond’s two-generation overlapping model, this paper designs and builds the old-age service savings model with fiat money as the medium and the mutual time savings model with community currency as the medium respectively. The results show that: （1）The use of fiat money as the medium of savings inhibits people’s willingness to save for old-age services; （2）The introduction of community currency as the medium of time savings for the elderly not only enhances their incentive to save for old-age services, but also better adapts to the new normal of population aging; （3）Compared with fiat money, community currency is more suitable to act as the medium of mutual pension time savings. The research conclusions are as follows: As a financial innovation of the aging society, the introduction of community currency with national credit guarantee can overcome the limitations of the current time savings mode, achieve the optimization of idle endowment resource allocation beyond the family in the whole society, and realize the gradual transformation from family endowment to social endowment, in order to cope with the new normal of population aging. This paper will provide theoretical support and decision-making reference for the government to issue community currency with national credit guarantee.