The Physicochemical environment and phytoplankton in litopenarus vannamei ponds located in the diked tidal flat in Binhai New District, Shaoxing City, Zhejiang Province were surveyed respectively in 2016 and 2017. In these ponds, the salinity, dissolved oxygen, pH, total ammonia nitrogen (TAN), nitrite-nitrogen (NO2--N), nitrate-nitrogen (NO3--N), total nitrogen, total phosphorus, total organic carbon and C/N ratio were 0~2, 6.2~13.9 mg/L, 7.5~9.8, 0.00~0.72 mg/L, 0.00~1.70 mg/L, 0.18~4.77 mg/L, 1.74~6.08 mg/L, 0.20~2.72 mg/L, 1.88~42.57 mg/L and 10~39, respectively. A total of 42 genus of phytoplankton, which belonged to 24 families and 6 phylums, were observed from the ponds, where blue algae and green algae are dominant. The phytoplankton biomass was 0.15~2.30 × 107 cell/L, and Chl.a concentration was 2.62~37.24 μg/L. The Chl.a concentration was positively correlated to the biomass of blue algae. The NO2--N and NO3--N were negatively correlated to pH. Preliminary analysis suggested that the high mortality of litopenarus vannamei occurred in the ponds in 2016 might be attributed to high pH. Therefore, proper control of the biomass of blue algae and pH should be a way to improve the survival rate of litopenarus vannamei in these ponds.