On the basis of the study of the operation mechanism of the hydraulic system of the roadway drilling rig and the reference of the relevant theoretical data, the reliability block graph and mathematical modeling of the hydraulic subsystem were completed in this paper. Based on the reliability model of the hydraulic system, the calculation of the relative reliability was carried out. It was found that the oil pollution was the main mode of the hydraulic system failure of the drilling rig, through the results of the analysis. It provided theoretical guidance for improving the reliability of hydraulic system of roadway drilling rig.