This study taken Wuliangsuhai Lake as the research object to reveal the microbial community structure of lake sediments, elucidated the representative iron-reducing microorganisms and their abundance, investigated the seasonal differences in the impact of iron-reducing microorganisms on As-P migration and transformation during the ice-bound period and the summer, and the impact of P on As migration and transformation, with the aim of providing a basis for deepening the understanding of the environmental geochemical behavior of As in cold and arid regions and As pollution remediation, and providing reference for the water environmental protection of As pollution and eutrophication risks in dual-risk lakes. The results showed that the relative abundance of iron-reducing microorganisms during the ice-bound period was higher than that in summer. There were seasonal differences in the representative iron-reducing microorganisms. Bacillus and Geobacter were the dominant genera of iron-reducing microorganisms during the ice-bound period and summer, but Geothrix was also one of the representative iron-reducing microorganisms in summer, and Shiwanella was one of the representative iron-reducing microorganisms during the ice-bound period. The correlation analysis and PLS-SEM model results showed that the representative iron-reducing microorganisms that play a major driving role in As-P migration and transformation and their impact on As-P migration and transformation exist significant seasonal differences. In summer, although the abundance of Thermoanaerobium was small, the iron-reduction process driven by Thermoanaerobium（path coefficient=0.178）would affect the release of As and P from sediments to water to a certain extent. In addition, Bacillus could also promote the iron-reduction process（Path coefficient=0.115）and was the main driver of As-P mobility and transformation. During the ice-bound period, the more abundant Geobacter was an important driver（path coefficient=0.530）of As mobility, which had an important effect on the mobility and transformation of As-P, and the effect of Thermoanaerobium on iron reduction (Path coefficient=0.284）and As-P mobility and transformation was greater than in summer（path coefficient=0.178）.