In order to solve the problems of difficulty in entering the soil and slow planting speed when transplanting rapeseed in sticky soil, a single-parallel multi-stem type transplanting mechanism was designed for rapeseed seedling. This mechanism consists of a crank-rocker mechanism and a parallel four-bar mechanism. The short rod at the upper end of the parallel four-bar mechanism is fixed, and the long rod is connected with the crank through the connecting rod and swings back and forth with the rotation of the crank. After the trenching device completes trenching, the rapeseed seedlings are pushed in the horizontal direction to transplant. By establishing a kinematic model and carrying out motion simulation by Matlab, the key parameters of the mechanism such as the length of the rods and the forward speed are analyzed and optimized by the orthogonal test. The best combination of parameters is: the traveling speed of the implement is 0.4 m/s, the length of the long rod in the parallel four-bar mechanism is 400 mm, the length of the connecting rod is 150 mm, and the hinge point of the connecting rod and the long rod is 110 mm from the upper end. According to the program data, the theoretical plant spacing of the optimal group is 205 mm, and the seedling pushing distance is 70 mm. The soil tank test of the prototype showed that the average planting distance of the machine was 194.82 mm in actual operation, whose error rate was 7.18% compared with the plant distance of 200 mm required by agronomy. The machine was running stably and the transplanting effect was good.