In this paper, the correlation between chlorophyll a and some environmental factors including pH, temperature, dissolved oxygen, transparency, total phosphorus, total nitrogen, chemical oxygen demand and so on, was analyzed by regression statistical method, based on the investigation data in Dishui Lake from January to December in 2009. The spatial and temporal distribution characteristics of chlorophyll a were also analyzed.The results showed that the concentration of chlorophyll a ranged from 0.5 to 139.5 mg/m³ with the average value of （52.97±28.32） mg/m³.The highest concentration occurred in the period of April to June. Extremely significant differences of chlorophyll a existed between sampling site Ⅲ and VI, V, VI respectively and also between sampling site I and VI. In different sampling sites, the important environmental factors affecting chlorophyll a were different, thus different factors were chosen for the multiple stepwise regression. However, the relationship between lg(Y_Chl.a) and lg(X_TP) was positive, while that between lg(X_TN/TP and lg(X_TN/TP) was negative. The equations obtained were lg(Y_Chl.a)=2.146+0.530lg(X_TP)，lg(Y_Chl.a)=2.017－0.275lg(X_TN/TP), which were more practicable than the multiple stepwise regression equations.