The innovation of old age insurance system of China,practices the model of old age insurance with part accumulation,which acquired by combining social pooling with individual accounts.Interest rate has an important influence upon the balance of the income and expenses of the pension fund.Using of the mathematical model and the data of population model from 1990 to 2100,this paper figures out the changing quantitative relation between contributing rate and interest rate,and analyzes the interest rate’s influence on the balance of pension fund.Because the interest rate’s influence on basic old age insurance benefit is opposite to its influesce on individual accounts pension,it will decrease the interest rate’s influence on contributing rate and steady the balance of pension fund when basic old age insurance benefit combine with individual accounts pension in appropriate proportion.
