Coastal wetlands are sensitive and vulnerable areas to global climate change and anthropogenic pressures. To study the spatio-temporal differences and driving factors of phytoplankton communities in coastal wetlands, we collected phytoplankton samples from 14 sites for four seasons in the Yingwuzhou Wetland (YWW) and its surrounding urban canals (SUC). A total of 97 phytoplankton species belonging to 7 phyla were identified during the study period, most of which are Bacillariophyta and Chlorophyta. A total of 61 phytoplankton species (62.9% of total species) were identified in both sites. Besides, 19 species were only identified in the YWW, while 17 species were specific to SUC. The richness of phytoplankton species exhibited significantly seasonal changes, with species numbers ranked in summer (89 species)＞winter (68 species)＞fall(49 species)＞spring (42 species). There are 23 shared species in all seasons, 12 species only identified in summer, and 2-3 typical species identified in other seasons. More diverse seasonal succession was found in YWW than those in SUC in terms of biomass in phytoplankton community types. The communities in YWW showed a succession from Bacillariophyta type(spring) to Cyanophyta-Euglenophyta-Chlorophyta type (summer), to Cryptophyta type (fall), and to Euglenophyta-Chlorophyta type (winter). While in SUC communities showed the other pattern from Cryptophyta-Bacillariophyta type (spring), to Cyanophyta-Euglenophyta-Pyrrophyta type (summer), to Cryptophyta-Bacillariophyta type (fall), and to Cryptophyta-Bacillariophyta type (winter). Seasonal dominant species varied significantly in both YWW and SUC. The dominant species of phytoplankton community in YWW were Aphanocapsa elachista and Chroomonas acuta, while the main dominant species of phytoplankton community in SUC were Cryptomonas erosa, Chroomonas acuta, Aphanocapsa elachista, Oscillatoria curviceps, and Melosira granulata. Statistical analyses revealed water temperature（WT）, dissolved oxygen, secchi depth, salinity, and nutrients were the main physicochemical factors regulating the distribution of phytoplankton communities in this area. Salinity was the key factor in distinguish the phytoplankton community in the YWW from SUC. WT and NH₃-N were the key factors in differentiating phytoplankton communities in different seasons. Variance partitioning analysis showed that the explained variance by environmental factors to the functional divergence (18.8%) was significantly higher than to the Shannon-Wiener diversity index (10%), which indicated that environmental filtering on niches was stronger than filtering on individuals. The functional evenness was not significantly influenced by the environmental factors but was significantly influenced by the temporal factors, which were possibly related to climate change, trophic structure shift of aquatic ecosystems, or biological interaction alter of seasonal plankton communities. The functional richness of both sites indicated that fall was most vulnerable to the disturbance, and the resilience of the wetland was significantly higher than that of its surrounding canals. The explained variance by environmental factors to the functional richness (41.2%) was significantly higher than to the species richness (16%), which indicated that functional richness was more sensitive to environmental changes than species richness. This study may provide scientific references for biodiversity conservation, ecosystem function restoration, and management in coastal areas.