Abstract: This study explored the nitrogen-fixing microbial community structure, diversity and nitrogen fixation activity in urban landscape water body, and the nitrogen-fixing contribution of nitrogen-fixing cyanobacteria in water from Muye Lake and People’s Park in Xinxiang city. Physical and chemical indicators are eutrophic in these two lakes. This study measured 16S rDNA and Nitrogenase nifH gene of microorganism by high-throughput sequencing, and determined nitrogen fixation rate of nitrogen fixing microorganisms in two lakes by the acetylene reduction assay. A total of 32 phyla and 275 genera were detected in the prokaryote groups, and a total of 9 phyla and 66 genera were detected in the nitrogen-fixing microorganisms in Muye Lake. A total of 31 phyla and 238 genera were detected in the prokaryote groups; a total of 4 phyla and 13 genera were detected in the nitrogen-fixing microorganisms in the water column of the People’s Park. Nitrogen-fixing cyanobacteria accounted for 3% in the Muye Lake and 9.3% in People’s Park. The richness of Nitrogen-fixing microorganisms in Muye Lake was significantly higher than that of People’s Park. The nitrogen fixation activity in the two lakes was similar. It is speculated that nitrogen fixation activity may be inhibited in eutrophic water.