On the basis of statistic data from 1984 to 2004 and regression analysis of influencing factors of foreign exchange reserves(FER),this article comes to the conclusion: current accounts,capital accounts,real GD Pshow remarkable positive correlation with the demand of FER,and exchange rate shows inverse correlation with the demand of FER,while foreign loans balance and FER show little correlation.On addition,the article analyzs the trend of(China's) FER fluctuation and clarifies the interaction of the trend and remarkable interpretative variables.