With the continuous improvement of living standards, China's mortality rate is gradually reduced. Nowadays, the aging population phenomenon is becoming more and more important. The mortality has always been the focus. On the basis of the Lee-Carter model, I compared several methods for the Lee-Carter model parameter estimation, and used China's 1990-2009 data to analyze by using the relatively simple model. Due to the default of the data, there are some errors in parameter estimation. In this paper, the Lee-Carter has been improved; I use random process to describe the parameter t k . The study found that the increase in life expectancy resulting from declining mortality has brought great pressure to China's pension system and give some advice on how to deal with longevity risk.