Abstract: In view of the fact that small plots and more slope plots restrict corn mechanized harvesting in hilly region of China, a crawler corn harvester was designed to realize corn mechanized harvesting under complex terrain conditions in hilly region. In order to ensure the ear-catching rate, the key parameters were designed and the optimal parameters combination was obtained that the diameter of the ear picking roller is 82 mm, the height of the spiral ridge on the surface of the ear picking roller is 8-15 mm, the length of the long ear picking roller is 50-60 cm, and the spiral angle of the ear picking roller is 20.79°. It can solve the feeding problems of corn plant in the complex terrain and the unsmooth feeding performance of traditional ear-picking roller, increase the feeding amount of header, and effectively shorten the length of the whole machine by about 0.5-1.2 m. Through structure simplification and mechanical analysis, it was concluded that the turnover of corn harvester working on the slope is related to the gravity position and the track span, and the turnover angle becomes smaller with the increase of the center of gravity of the equipment, that is, the turnover risk is greater when working on the slope ground. Therefore, adjusting the width between the two tracks can increase the safety range of gravity variation of the whole machine, reduce the rollover risk of the machine working on the slope. The running stability of the whole machine in the complex terrain conditions can be improved by 27.34% when the width between the two tracks expands with 0.8 m. The hydraulic system of 10 t engineering vehicle was used to solve the problem of driving load in slope operation and the resistance in harvesting operation, which will directly affect the function of the whole machine in the field, such as walking, overtaking and steering. Based on the principle of hydraulic control, a two-way operation control system was developed, which can meet the turning and turning requirements in small plots such as mountains and hills, and improve the turning efficiency of the whole machine by more than 90%. Zhengdan 958 maize cultivars with grain moisture content of 33.5%, stem moisture content of >89% and fruit stalk moisture content of >52% were selected to test ear loss rate. The assessment indices of influencing factors of ear loss rate were determined by orthogonal test, including machine forward speed, ear picking roller clearance and ear picking roller speed. The mathematical regression model between the influencing factors and indicators was established by using Design Expert, and through the analysis of variance to verify the significance of the assessment indicators, the best combination of operation parameters was determined that the forward speed of the machine is 2 km/h, the clearance of the ear picking roller is 14 mm, and the speed of the ear picking roller is 1 000 r/min. Under the optimal combination of the operation parameters, the ear loss rate was 1.25%. The design indicators of the machine can meet the relevant national standards, and can satisfy the needs of corn mechanized harvesting in hilly and mountains region.