Abstract: The clutch of transplanting mechanism was detached and thus the rice transplanting was unable to continue when transplanting mechanism contacted the hard objects such as stone and metal.The miss of seedling transplanting happened if the hard objects in seedlings was not detected in time.In order to break through this technical bottleneck, a low-cost, intelligent and real-time monitoring system for stone in seedlings was developed.To improve the adaptability of monitoring system to dusty and muddy environment, a self-cleaning device based on transparent dust cover and nozzles was designed, which decrease the interference from dust and muddy and increase the sensor accuracy.The hardware and software algorithm were developed for stone detection, sound-light alarm, self-cleaning dust control and so on.The real-time detection for stone and corresponding alarm, monitoring for the remaining seedling amount in seedling box and the calculation of practical transplanting area were meanwhile realized under complicated working environments.Experimental results showed that the monitoring accuracy of the system for rocks and other hard objects in seedlings was 94.4%,the relative error for monitoring the amount of remaining seedlings and the actual area of seedling transplanting were less than 7.9% and 4.48%, respectively.The system has strong anti-interference and reliability to the muddy water environment in practical field conditions. The designed monitoring device can be applied to artificial driving rice tranplanter and unmanned transplanter, which provide theoretical basis and practical experience for detection of working status parameters on unmanned transplanter.