Jinshan City Beach is an artificial lagoon in Hangzhou Bay of the East China Sea, which is the first coast national AAAA level scenic spot in Shanghai. In order to control the water quality of Jinshan City Beach based on the complex physical oceanographic properties of lagoons, ecological restoration has been carried out in recent years. From 2016 to 2018, the relationship between phytoplankton community succession and environmental factors in this artificial lagoon was investigated for three consecutive summers. The results showed that the number of phytoplankton species increased in summer from 2016 to 2018(109 species of 7 phyla), the species of Bacillariophyta, Cyanophyta and Chlorophyta were dominant. A total of 13 dominant genera were found. The more dominant genera were Microcystis, Trachelomonas, Melosira and Cyclotella. Among them, Microcystis was the most dominant genus in summer, the overlap of other dominant genera was small. From 2016 to 2018, the abundance of phytoplankton varies greatly, ranging from 50.78×10⁴-5 957.52×10⁴ cells/L, 5.35×10⁴-25.67×10⁴ cells/L to 474.87×10⁴-1026.94×10⁴ cells/L respectively, of which Microcystis abundance was the largest, accounting for 97.88%, 68.18%, and 77.23%, respectively. During the survey, the diversity index (H') and evenness index (J') of phytoplankton increased and then decreased, but generally showed an upward trend, while the dominance of the first dominant genus generally decreased, which indicated that after ecological restoration, the phytoplankton community in Jinshan artificial lagoon was in a positive succession, and the ecological risk tended to decrease. RDA result showed that total nitrogen, total phosphorus, ammonium, nitrite, soluble reactive phosphorus and silicate were important environmental factors affecting phytoplankton community. Among them, silicate, nitrite, ammonium and soluble reactive phosphorus are more relevant to the phytoplankton community of the lagoon.