Abstract: Nowadays,Bositeng Lake is the biggest inland fresh water lake in China. However,the mineralization degree of the lake had preponderated over 1.0 g/L since 1970's,1.8 g/L in 1980's,and now about 1.3 g/L. Based on the observation data,the variable trend of mineralization degree of the lake is discussed in this paper. The main and key factors that influence the mineralization degree of the lake are analyzed and decided by the water quantity-quality-ecology system model. Finally, countermeasures about mineralization control are put foreword.