As one of the important parts in the intelligent construction of the whole rapeseed industrial chain, the unmanned seeding operation of rapeseed can greatly improve the operation accuracy and labor production efficiency, and achieve the effect of reducing costs and improving efficiency. The middle and lower reaches of the Yangtze River are the main producing areas of winter rapeseed in China. In the process of unmanned seeding operation, linear navigation is the main method, and field U-turn and line-feed play a key linking role, and the U-turn path planning and controlling effect directly affect the line-to-ine accuracy. Affected by the land and previous crops in Southern China, especially in the rice-oil rotation area in the middle and lower reaches of the Yangtze River, the land scale is small and the soil is sticky. The unmanned planting operation process is complicated at the head of the field, and the U-turn is easy to slip when making the U-turn, and it is easy to produce deviation after changing the line. The tractor start the next row of seeding operations before it goes on the working line, resulting in poor row alignment accuracy and the phenomenon of replay and missed seeding, which directly affects the quality of rapeseed seeding operations. Aiming at the problems of complex line-feeding and poor accurate line-to-line ability of tractor navigation during unmanned seeding operation, a two-back and three-cut fishtail U-turn model was proposed to find the line. Analyzing the characteristics of unmanned seeding operation and equipment characteristics of the rapeseed direct seeding unit, and taking quantitative analysis in the line-hunting path at the U-turn at the field head, a set of rapeseeds unmanned seeding operation system was constructed, the main parts included CaseTM1404 tractor, Beidou high-precision positioning system, angle sensor, vehicle controller, CAN analyzer, industrial computer, electronically controlled steering wheel and rapeseed precision seeder. The simulation test of three kinds of fishtail turning models was carried out. The results showed that the area of the non operating area of the two-back and three-cut fishtail U-turn model was reduced by 14.62%~22.43% compared with the traditional fishtail U-turn model. The field unmanned seeding operation experiment of the model controller was carried out, and the results showed that the initial offset distance and rising time of the two-back and three-cut fishtail U-turn model was reduced by 7.37~8.08cm and 1.3~2.3s compared with that of the traditional fishtail U-turn model, and the operation alignment accuracy was 1.48cm. This research result had guiding value for the comb-path U-turn operation during unmanned seeding operation of rapeseed.