Metaphytic blooms are caused by the overgrowth and the aggregation of filamentous green algae, and are one of the environmental problems in Lake Ulansuhai. This study tracked the trend of water quality and metaphytic blooms area in Lake Ulansuhai during 1986-2021 based on data integration and remote sensing image interpretation of Landsat TM/OLI satellite. Environmental factors influencing the interannual changes of metaphytic blooms area were analyzed using Pearson correlation analysis and multiple linear regression analysis. The results indicated that although the concentrations of COD_Cr, total nitrogen(TN) and total phosphorus(TP) had decreased significantly, Lake Ulansuhai was still eutrophic (TLI(Σ)>50). Metaphytic blooms area was positively related to the concentrations of TP, TN, NH₃-N and temperature, but was negatively influenced by outflow volume, wind speed, the area of submerged macrophyte and inflow volume. The multiple linear regression showed that the area of submerged macrophyte and outflow volume were the main factors influencing the area of metaphytic blooms in Lake Ulansuhai. During the ecological hydration period (2009-2021), the concentrations of TP and TN, as well as the area of submerged macrophyte, declined with the increase of outflow and inflow volume. As a result, the expansion trend of metaphytic blooms was suppressed. Moreover, the current condition of nutrition and submerged vegetations in Lake Ulansuhai are still suitable for the growth of epiphyton and metaphytic blooms, and the rising temperature and weakening wind may intensify the metaphytic blooms in Lake Ulansuhai in the future. Multiple means are recommended for preventing and mitigating metaphytic blooms, including ecological hydration, external nutrient reduction, submerged macrophyte management, and water flow enhancement.