Abstract: The paper introduced a new type of online checking and signing method of sensor in safety monitoring and control system of coal mine. Before online checking and signing one sensor, personnel for checking sensor could make checking and signing setting by sensor, substation and main computer, and made the system automatically identify the sensor was in checking and signing state, namely measured value of the sensor later was checking and signing value, not actual value. After finishing checking and signing task, personnel for checking sensor could relieve checking and signing setting by sensor, substation and main computer at once to make the system renew normal working state as quickly as possible.