Abstract: [Objective] The Jimsar area in the southern margin of Junggar Basin is rich in low-medium rank coalbed methane(CBM) resources, showing obvious characteristics of microbial gas. Up to now, it is not clear whether there is active supply of microbial gas in Jimsar area, which restricts the evaluation of CBM resource potential and the next exploration deployment in this area. [Methods] In this paper, the water samples of CBM development wells and the coal samples of adjacent CBM parameter wells in Jimsar area are taken as the main research objects, and the actual coal reservoir medium environment is taken as the constraint condition. An anaerobic fermentation gas production simulation device under near in situ conditions was constructed. Based on the comparative analysis of gas production characteristics, pore volume and pore size changes of coal samples, microbial community structure evolution, and microbial gene function characteristics at different stages, the gas production potential and metabolic mechanism of in situ microorganisms in Jimsar area were discussed. [Results] The results showed that the in situ microorganisms in Jimsar area had the potential to produce microbial gas under the current conditions, and the cumulative gas production of CH4 in the experiment was 9.49 × 10-2 ml/g. It can be seen from the metagenomic sequencing that there are many types and high abundances of hydrolytic bacteria in the in situ microorganisms of Jimsar area. The typical acidogenic fermentation bacteria and hydrogen-producing acetogenic bacteria are relatively few, and the methanogenic archaea are mainly Methanosarcina. Although there are relatively few acidogenic fermentation bacteria and hydrogen-producing acetogenic bacteria, most of the hydrolytic bacteria can directly degrade the macromolecules in coal into short-chain fatty acids, acetic acid, hydrogen and carbon dioxide, which can provide sufficient substrates for methanogenic archaea. [Conclusion] In the early stage of anaerobic fermentation, Aliarcobacter rapidly proliferated and inhibited hydrolytic bacteria such as Pseudomonas. The functional abundance of carbohydrate metabolism,xenobiotics biodegradation and metabolism decreased, and the hydrolysis process was limited, which could not provide sufficient substrates for methanogens. The abundance of methanogen Methanosarcina decreased, and the amount of methane produced in the stage decreased. Subsequently, the abundance of Aliarcobacter decreased, the metabolic activity of hydrolytic bacteria was reactivated, the functional abundance of carbohydrate metabolism and xenobiotics biodegradation and metabolism increased, the substrates available for methanogens in the system were enriched, the abundance of methanogen Methanosarcina increased, and the amount of methane produced in the stage also increased simultaneously. The research results can provide theoretical basis for the evaluation of low-medium rank CBM resources, the formulation of exploration plan and the smooth implementation of coalbed gas bioengineering.