Abstract: In order to study the coalbed methane development characteristics of coal reservoir under the pollution of drilling fluid, taking Shizhuangnan block in the south of Qinshui basin as the research object.Based on the calculation model of permeability damage ratio, the damage degree of drilling fluid to coal reservoir is calculated.On this basis, the reservoir types are divided, and the clay content and the proportion of broken coal thickness of different coal reservoirs are analyzed.The development characteristics of coalbed methane in different coal reservoirs after drilling fluid pollution are analyzed.The results show that the coal reservoir can be divided into three types:light pollution, heavy pollution and serious pollution.The average ash content of the seriously polluted coal reservoir is 17.69%, and the average proportion of the thickness of the broken coal is 76.47%.During the fracturing operation, the drilling oil pressure curve will decline greatly, the crushing pressure is small when it is stable, and the single-phase flow stage time is long when it is discharged.The average ash content of slightly polluted reservoir is 10.07%, and the average thickness of crushed coal is 34.85%.The overall oil pressure curve is relatively stable, the decline range is not obvious, and the single-phase flow stage time is short.The average ash content of the heavily polluted reservoir is 13.04%, and the average proportion of the thickness of the broken coal is 59.65%.The oil pressure curve is similar to that of the easily damaged drilling, but the decline range is smaller than that of the easily damaged drilling, the crushing pressure required for stability is higher than that of the easily damaged reservoir drilling, and the single-phase water flow stage time during drainage is between the two.