An inequality model was proposed to correct the intersection and separation of working contours of matching teeth under equality model, which should not take place in real eccentric involute gear transmission. When 5000 coordinate points of involutes working contours of benchmark tooth were determined to compute the inequality model, the coordinate control precision of searching meshing points can reach 0.001 mm and the angle error can reach 0.001°. Computation showed that the angle error will become bigger with the increment of gear eccentricity, and be exaggerated gradually when multistage eccentric involute gears drive. The inequality model may solve accurately relative motion relationship between gear box and planting arm, and its accurate position and posture can be obtained when seedling-claw takes seedlings from seedling box and pushes seedlings into soil. Angle values of driven gears round both sides of the center gear are not equal with driving gear angle at the 180°, which results in path misalignment of seedling-claws fixed on forward planting arm and backward planting arm. Simulation result of ADAMS software validated that the solutions of the inequality model were correct. The path error was less than 1.01 mm when gear eccentricity was 0.1043. 