To study the impacts of super-large floating photovoltaic (FPV) power plants on the key indicators of the water ecological environment in the coal mining subsidence water area in Huainan, China, the key water ecological indicators of lakes and surrounding water bodies with different photovoltaic panel coverage rates were monitored and analyzed in different seasons. Based on contrasting and analyzing the concentrations of typical water ecological indicators of chlorophyll and phycocyanin, common water quality parameters, and heavy metal element concentrations with mathematical statistical methods, it was found that the coverage of photovoltaic panels weakened the correlation between water ecological indicators and nutrient indicators, and reduced the utilization rate of nutrients by phytoplankton in the water body, and FPV with a coverage rate of about 50% could prevent further eutrophication of the water body; the concentrations of heavy metal elements were very low in the whole area, and the photovoltaic modules laid on water did not increase the concentrations of heavy metal elements in the water body. The construction of FPV power plants in large-scale coal mining subsidence water areas similar to those areas in Huainan is an important direction that is worth exploring for the improvement of the ecological environment and efficient development and utilization of abandoned mines.