It was necessary to maintain appropriate height of stubble according to the characteristics of variety in the first season of harvesting ratoon rice to ensure successful regeneration in the second season. Frequent adjustment of the header height was often required due to the uneven field terrain when harvesting ratoon rice with grain combine harvesters existed in China. The operation of harvesting is manually performed by the operator， both increasing the intensity of labor and constraining the efficiency of harvesting. An adaptive adjustment system of header height for a ratooning rice combine harvester was designed to improve the quality and operational efficiency of harvesting ratoon rice. First， a structural model of the header copying wheel for adjusting height was established. Second， the hydraulic system of a 4LZ-1.6Z grain combine harvester was modified and optimized， and a simulation model of adjustment system was developed using Simulink to compare and analyze the performance of classical PID and fuzzy PID control strategies. Then， performance was verified using response accuracy and response speed as indexes of experiment. The results showed that the mean absolute error for classical PID control and fuzzy PID control was 17.3 mm and 10.5 mm， respectively. The average value of response speed for classical PID control during the lifting and lowering the height of header was 0.185 m/s and 0.213 m/s， respectively， whereas that for fuzzy PID control was 0.202 m/s and 0.219 m/s. Finally， the results of conducting a field experiment on uneven terrain based on the fuzzy PID control showed that the header height remained stable at approximately 500 mm， with a mean deviation of 6.81 mm and a stability coefficient of variation of 1.62%， indicating that the proposed control strategy had good stability and performance of tracking. It will provide an effective technical solution for adjusting header height in the mechanical harvesting of ratoon rice and a practical value for improving the quality and operation efficiency of harvesting.