Aiming to automatic guidance operation of the combined direct seeding unit for rapeseed in the scene of unmanned farm, a generally applicable path planning algorithm for rapeseed direct seeding operation in convex polygon boundary field was put forward. Based on the basic requirements of path planning algorithm for rapeseed direct seeding operation, the operation area was divided into internal direction parallel operation area and external contour parallel operation area, which were called direction parallel operation path and contour parallel operation path. The operation path was further divided into working path and non-working path, and the generated principles of the latter, including interline connection path, area connection path, corner connection path, entry path and exit path were introduced in detail. The optimal operation direction of the direction parallel path was obtained by minimum span method, and the operation sequence of the direction parallel path was optimized by greedy algorithm or Google OR-Tools. Considering the complete length of operation path, algorithm time consuming, repeated and missed area, aiming at the no-tillage or rotary tillage seeding operation of the combined direct seeding unit for rapeseed, taking Dongfanghong-LX804 tractor + 2BFQ-6 no-tillage direct seeder and other units as the object, the performance of algorithm was tested in four convex polygon boundary fields with different operation parameters, ground turning strategies and scheduling strategies. The test results showed that the coverage of rapeseed was more than or equal to 95.14%, the repeat rate was less than or equal to 2.63%, and the percentage of effective working path was more than or equal to 57.39%, the algorithm took time less than or equal to 8.003ms, which was proved stable and efficient, and satisfied the basic requirements of path planning for rape direct seeding operation.