Abstract: Based on the implementation of the Comprehensive Plan for Reducing Social Insurance Rates in 2019, this article establishes an actuarial model to predict the population changes from 2021 to 2050 in accordance with the data of the seventh population census and the latest family planning policy of the state. From the perspective of room for feasible fee reduction, it explores the impact of the comprehensive fee reduction reform on the fund balance of the employee's basic endowment insurancepayments under different assumptive conditions, such as the tracebackassumptions, the optimistic assumptions, the assumptions of fertility level improvement, the risk assumptions, and the expansion assumptions of comprehensive fee reduction reforms respectively. The findings show that the comprehensive reform of fee reduction can effectively alleviate the pressure of fund revenue and expenditure, but the higher the replacement rate and the longer the target time point, the weaker its effect will be.Reducing the replacement rate is the core of the fund balance of the employee' basic endowment insurance system and the formation of the room for feasible fee reductions. The inclusion of delayed retirement, partial transfers of state-owned capital and institutionalized financial subsidies into the comprehensive reform of fee reductions can effectively enrich the basic pension insurance fund, ensure the long-term balance of the pension insurance fund, and provide room for further fee reduction reforms. Then, further deepening the comprehensive reform of employee pension insurance premium reduction and determining a delayed retirement plan as soon as possible with the expansion of the premium base and fund income source can achieve the dual goals of balancing fund revenue and expenditure and alleviating corporate burdens.

Key words: comprehensive reform to fees reduction, fund balance, room for fee reduction, employee's basic endowment insurance