Aiming at the problems of seedlings-damaging due to the high seedling speed, and low uprightness due to the relative horizontal movement in the transplanting process, a fully automatic slide-track type dryland pot seedling transplanting mechanism was designed. The functions of seedling retrieval, transportation, planting and resetting were realized by the slide-track mechanism, so that the movement trajectory and movement speed in the process of taking seedlings and planting reached the optimal state. Based on the theoretical analysis of the transplanting mechanism, the kinematics model were established. The computer-aided optimization design software was developed by using VB software, and a group of mechanism parameters that met the requirements of the ideal transplanting trajectory was obtained. According to the mechanism parameters, the layout design of the transplanting mechanism was carried out, and the 3D modeling were completed. The kinematics simulation analysis of the transplanting mechanism was carried out by using ADAMS software, which verified the rationality of the mechanism design. The trajectory verification process was carried out on the physical prototype using high-speed cameras. Comparison results showed that the theoretical trajectory and the simulated trajectory were consistent with the working trajectory of the prototype, which verified the correctness of the mechanism design. The mechanism performance experiment was carried out under the condition of planting frequency of 62 plants/min, and the results showed that the average seedling success rate was 95%, the average planting upright degree of the seedlings was 82°, and the average uprightness of seedlings qualified rate was 93.4% which met the requirements of dryland pot seedling transplanting.