Abstract: Principal component analysis (PCA) and Canonical correspondence analysis (CCA) were used to investigate the relationships between environmental factors and phytoplankton of the Taiyuan Fenhe water reserve area in flooding season. Meanwhile, it studied the temporal and spatial distribution characteristic of chlorophyll concentration and the correlations between chlorophyll and other environmental factors. The results showed that chlorophyll concentration appeared some spatial and temporal difference in the Taiyuan Fenhe water reserve area, ranging from 5.83 to 181.00 mg/m³, and the mean chlorophyll value in July is higher than that of the other three months. The S8 sampling site reached to a maximum value at 181.00 mg/m³, whereas S1 has the lowest level of mean chlorophyll value. Significantly correlation was found between chlorophyll concentration and COD_Mn, COD_Cr, NH₄⁺-N, TP, N/P and pH. Principal component analysis indicated that the factors affected the environment of Fenhe water reserve area including phytoplankton biomass, organic matters, nitrogen and phosphorous nutrients, hydrologic and meteorological conditions as well as photosynthesis intensity of water. Chl, COD_Mn, COD_Cr, and TP had significant effect among them. Through Canonical correspondence analysis, there was some difference of relative abundance among Cyanophyta, Chlorophyta and Bacillariophyta, but insignificant difference of spatial distribution. It was also revealed that the different correlations between environmental factors and sampling sites.