In view of the phenomenon of "big engines and small standards" existing in Chinese fishing vessels and the lack of corresponding monitoring means, the on-line monitoring system of the main engine power of fishing vessels was  studied. Magnetoelectric speed sensor and strain type torque sensor are used to measure the speed and torque of the main engine of fishing vessels. Signals collected are transmitted by a wireless telemetry system, and the power value is obtained by computer processing, realizing the online monitoring, recording and replaying of the main engine power of fishing vessels. The Weichai WP10C287-21 diesel engine was selected for testing based on its propulsion characteristics, and the measured values were compared with the calibration values. Results show that the power measurement error rate of WP10C287-21 diesel engine was  less than 1% of the calibration power range, implying that the system can generally realize the accurate on-line monitoring of main engine power of fishing vessels. This study provides a reference for relevant units to collect information on the main engine power of fishing vessels, manage the fishing activities of fishing vessels and optimize the vessels’ machine and propeller matching.