The development of automatic monitoring system for core filling rate is to fill the shortage of core condition monitoring in the coring process. The automatic monitoring system is composed of main controller， reserved temperature and pressure monitoring module， Hall sensor module， data storage module and serial debugging module. Among whcih， the principle of core status monitoring is based on Hall effect. The coring speed range of the system can be monitored in 0~30 mm/s， and the monitoring accuracy is about 1%. The system uses STM32 single-chip microcomputer， large-capacity memory， high-speed USB interface and so on， which has the functions of online debugging， programming and upgrading. The sea tests were made， and the results show that the system can automatically monitor the process of core penetration into the core tube at a water depth of 3000m （a hole bottom pressure of 0~35MPa）， which can provide theoretical guidance for the selection of field sampler type and the optimization of working parameters of the sampler， and has a broad application prospect.