Abstract: Because of the poorness and complexity of the coal mine underground and lacking of effective condition monitoring equipment in a long time, the “black box”, an recorder installed on the roadheader which of long continuous working hours and large storage, has been invented and used, and it could monitor and store working conditions of roadheader. Based on the data that “black box” recorded in the underground, torque of the cutting head could be derived by the combination of this data, voltage, current and other roadheader parameters. The one-dimension load spectrum of cutting head could be drawn on the basis of time domain. The static load component could be determined by the analysis on the mentioned load spectrum. Furthermore, according to the rain flow count method, the two-dimension load spectrum could be drawn. After analyzing the above mentioned image, the value of the static load and the range of dynamic load are accessible.