Urban wetlands play an increasingly crucial role, and the health assessment of their ecosystems is an important process that helps us understand the current condition of wetlands and take appropriate protective measures. To explore the ecological health status of the Lhalu Wetland and its relationship with water environmental factors, phytoplankton samples were collected and water environmental factors were measured in the main water systems of Lhalu Wetland in July (summer), October (autumn) 2021, and May (spring) 2022. Phytoplankton species were identified and their cell abundance and biomass were calculated. The ecological health status of the wetland was evaluated using the morphologically -based functional group (MBFG), Water Quality Index (WQI), and Phytoplankton Index of Biotic Integrity (P-IBI). The spatiotemporal distribution characteristics of water quality and morphologically -based functional group, and the correlation between P-IBI values and water environmental factors were analyzed. The research results show: (1) Based on the Water Quality Index (WQI) values, the overall water quality of Lhalu Wetland is evaluated as "good to moderate," with spatial and temporal variations in water quality: spring is superior to autumn, which in turn is superior to summer, and the eastern part is superior to the western part. (2) Based on the Phytoplanktonic Index of Biotic Integrity (P-IBI) values, the overall water ecological health status of Lhalu Wetland across three seasons is evaluated as "health to sub-health," with the spring water ecological health status being superior to autumn, which is superior to summer, and the central-eastern sampling points are generally superior to the south-western and north-eastern parts. (3) The Phytoplanktonic Index of Biotic Integrity (P-IBI) values show a significant positive correlation with the Water Quality Index (WQI) values (P < 0.05), and the evaluation of the water ecological health status of Lhalu Wetland based on P-IBI is closely consistent with the results of WQI evaluation. Dissolved oxygen (DO) is the main water environmental factor affecting the water ecological health status of Lhalu Wetland (P < 0.05), and temperature, water volume, human activities, and land use types are important factors affecting the water quality and water ecological health status of Lhalu Wetland. (4) In spring, the abundance of functional groups "Ⅰ" and "Ⅲ" increases as the water ecological health status of Lhalu Wetland declines. In summer, the ecological health status of the water body has little relationship with the changes in the abundance of functional groups. In autumn, the increase in the abundance of functional groups "Ⅲ" and "Ⅶ" is significantly associated with the decline in the ecological health status of the water body.