Abstract: In order to meet the demands of modern breeding, plant protection and cultivation management, high-throughput crop phenotype information acquisition has become a current research hotspot. A self-propelled crop phenotyping platform was designed to improve the scalability, generalizability and flexibility of phenotyping platform. The platform body adopts a frame structure and uses 4 BLDC motors to realize 4 independent driving wheels, and the control system was constructed in the mode of 1 main control chip and 4 sub-control chips. The online self-tuning PID control method was designed based on the relay feedback to achieve the PID Parameter online self-tuning and platform speed control, and designed no-load and ground-load comparison test. The test results show that under no-load and ground-load conditions, the system can operate within 0.169～0.0.468 s at different set speeds to reach a stable state, with high adjustment speed and accuracy.Under ground load conditions, the speed is adjusted directly using the parameters obtained by tuning at no load and those obtained by retuning after load. The error between the two is less than 0.08 s at different speed requirements. This proves that the parameters after tuning at no load can be directly applied to the actual speed control of the phenotyping platform.