Abstract: Aiming at the problem of abnormal CO gas and unclear source type in 160205 working face of Yangchangwan Coal Mine, the source of CO gas in working face was comprehensively analyzed through borehole test in deep coal body, temperature and CO distribution test in goaf, CO distribution test in working face, coal crushing experiment, temperature programmed experiment and normal temperature oxidation experiment. The results show that there is no CO gas in the original seam of Yangchangwan 2^# coal. Coal crushing in nitrogen atmosphere and air atmosphere can generate CO gas, and with the extension of crushing time, the amount of CO gas produced presents a rising trend. When the residual coal temperature in goaf is lower than 50 ℃, CO in working face mainly comes from low temperature oxidation of residual coal in goaf and normal temperature oxidation of coal behind frame and working face, followed by CO gas generated by coal machine cutting and breaking operation in coal mining process.