Abstract: According to problem that drilling parameters cannot be directly monitored and stored in real-time and centralized display in the drilling process of full hydraulic tunnel directional drilling rig in coal mine, in order to meet the precise control of directional drilling process and optimization of drilling parameters in coal mine, based on the research purpose of generality, stability and expansibility, the drilling parameter monitoring system for directional drilling rig in coal mine based on PLC is developed, which has many functions such as real-time monitoring of drilling parameters, automatic data storage, remote data transmission, graphical display of parameters, condition recognition and failure alarm. In order to verify performance and reliability of system, a performance test of the system is carried out, after that a field test is carried out combined with high-power directional drilling rig in Baode Coal Mine,Shenhua Shendong Coal Group. The test results show that the parameter monitoring system can be quick installed and stable in operation, and all kinds of drilling parameters can be accurately monitored during the drilling process while the measurement error is less than 1.25%, and the drilling parameters can be stored in the backstage database in real time. At the same time, the system will alarm while the drilling process and condition of the drilling machine are abnormal. The application of the system can effectively improve the quality of drilling borehole and prevent drilling accidents in the borehole, which will play an important role in optimization of technological parameters and theoretical study of directional drilling in coal mine, and provide technical support for mechanization, automation and intelligent development of directional drilling equipment in coal mine.