Aiming at the problem of injured seedlings caused by poor vision of drivers in the operation of plant protection machinery in high ground clearance, a method of assistant driving was proposed. A high-gap plant protection machine was taken as the research object, and a man-machine aided driving system was designed. Firstly, the hydraulic system design of the auxiliary driving system was elaborated in detail, on this basis, the structure of the steering system was improved. Secondly, based on preview algorithm and two-degree-of-freedom vehicle steering model, the front wheel angle control of steering system was studied. Finally, the control system software was created based on LabVIEW. The software control system included speed control system, navigation and positioning system and steering control system. Under the condition of 0.5m/s speed, the experiments were carried out on cement pavement and maize dryland respectively. The test results showed that the average linear path tracking error of auxiliary driving system was 5.2cm and the standard deviation was 3.4cm under cement pavement condition, and the average tracking error of auxiliary driving system was 6.8cm and the standard deviation was 4.8cm under the driving condition of corn crop between lines. Based on the above test data, it was concluded that the plant protection machinery auxiliary driving system met the field driving requirements. The auxiliary driving system designed had good practicability in wide-line crop cultivation.