In this paper, the enterprise annuity replacement rate in China is discussed. The enterprise annuity replacement rate refers to the ratio of pension income and wages income before retired. It is an important indicator to measure the standard of living of the elderly population. The paper succeeded derived the equilibrium model of the enterprise annuity fund under the cost and management fee, and the enterprise annuity replacement rate is deduced. Moreover, the sensitivity analysis of each parameter is given, and the enterprise annuity rate of substitution for different gender is also obtained, which shows that the existing system of enterprise annuity unfairness to exist between men and women.