Abstract: Chlorophyll a (Chl-a), physical and chemical factors of water samples in the 13 estuaries of Gehu Lake were monitored and analyzed monthly for 2 years from January 2018 to January 2020.The spatio-temporal characteristics and their correlation with major environmental factors were studied such as water temperature, pH and nutrients. The results show that: (1) ρ(Chl-a) changed significantly over time, with the highest in summer, followed by autumn and winter, and the lowest in spring; (2) In terms of spatial distribution, ρ(Chl-a) in the estuary area of the northwest was significantly higher than that in the south of Gehu Lake; (3) ρ(Chl-a) is extremely significantly positively correlated with water temperature, pH, and permanganate index (COD_Mn), negatively correlated with DO, and had no significant correlations with ρ(TN), ρ(NH₄⁺-N), ρ(NO₃^--N), ρ(PO₄^3--P) and ρ(DOC). The logarithm of ρ(Chl-a) had a significant positive correlation with the logarithm of TP, and a significant negative correlation with the logarithm of N/P ratio; (4) Phosphorus was the main determinant of ρ(Chl-a) in the estuary area of Gehu Lake. The results can provide reference for the water environment treatment of Gehu Lake.