Abstract <p>The salt lake ecosystem, characterized by extreme environmental gradients, harbors microbes that uniquely adapt to high salt stress through natural selection. However, how abiotic and biotic factors shape the microbial community assembly in Yuncheng Salt Lakes remains unclear. Here, we investigated the assembly processes and meta co-occurrence patterns of microbiota in both water and sediment sampled from 14 distinct wide range of salinity lakes in the Shanxi Yuncheng area, Midwest of China, using 16S rRNA and 18S rRNA gene sequencing technology combined with multivariate ecological and statistical methods. Habitat differentiation led to the differences in microbial diversity, co-occurrence patterns, and community assembly between sedimentary and planktonic communities. Sedimentary prokaryotes were more shaped by deterministic processes than planktonic bacterial communities. Salinity was a major abiotic factor influencing the balance between stochastic and deterministic processes in both sediment and water. Enhanced microbial interactions within sediments exhibited a more prominent impact in shaping community assembly, as indicated by the stronger association between network-inferred species and prokaryotic βNTI. Moreover, we revealed significant differences in how core species concerning βNTI responded to biotic and abiotic factors. Our findings elucidated the ecological process underlying microbial communities in Yuncheng Salt Lakes and shed light on the mechanism of microorganisms to maintain community complexity and diversity in the extreme environment.</p> Key points <p><i>• Sedimentary prokaryotes were more shaped by deterministic processes than planktonic prokaryotic communities.</i></p> <p><i>• Salinity was a major factor influencing the balance between stochastic and deterministic process.</i></p> <p><i>• Inter-domain and intra-domain symbiotic interactions within sedimentary communities represent key biotic factors influencing their community assembly.</i></p> Graphical abstract <p></p>