For the large monopoly wide potato cultivator due to the width of the larger, equipment structure was huge and the potato biologica morphological characteristics of the longitudinal and horizontal stability of the potato poor, serious deflection, pressure seedling injury and other problems,the optimized design and test of the large monopoly wide potato cultivator were carried out. Through kinematic analysis of the potato cultivator, the main factors affecting the longitudinal and lateral stability of the tiller was determined and the design of its components was optimized, the EDEM discrete element simulation software was used to conduct a secondary orthogonal rotation simulation, test with the horizontal distance from the mulching share to the hinge point of the parallel four-bar and the frame, the lateral width of the parallel four-bar and the operating speed as the test factors, and the monopoly straightness and the monopoly height stability coefficient as the evaluation indexes. Using Design-Expert 11.0 software to optimize and analyze the results of the simulation test. When the horizontal distance from the mulching share to the hinge point of the parallel four-bar and the frame was 702.7mm,the lateral width of the parallel four-bar was 255.4mm and the operating speed was 1.29m/s, the monopoly straightness of the cultivator was 2.39cm and the stability coefficient of the monopoly height was 94.12%.The optimized data were verified in field tests, results showed that the straightness of monopoly direction was 2.4cm, the pass rate of cultivation was 95.7%, the injury rate was 1.5%, the stability coefficient of monopoly height was 94.2%, and the height of cultivation was 7.8cm. The optimized large monopoly wide potato cultivator was more reasonable, with good working effect,which had better longitudinal stability and lateral stability than the pre-optimized large monopoly wide potato cultivator.