In view of the problem that the existing vegetable transplanting mechanisms cannot precisely achieve the required transplanting trajectory and posture for the integrated operation of transplanting and harvesting, a hybrid six-bar single-degree-of-freedom vegetable pot seedling transplanting mechanism was proposed based on non-circular gear constraints. According to the requirements of integrated transplanting and harvesting, an ideal transplanting trajectory integrating the static trajectory of taking seedlings and the dynamic trajectory of planting seedlings was determined as an “eagle-beak-shaped” static trajectory and an “approximate straight-line-shaped” dynamic trajectory. The kinematic model of the transplanting mechanism was established. The non-circular gear transmission function was constructed by using quintic B-spline interpolation method. Considering the agronomic requirements of vegetable transplanting, the spectral clustering balanced differential evolution algorithm (SCEDE) was used to optimize the design of the transplanting mechanism with the minimum motion error and the optimal gear curve of the non-circular gear as the optimization objectives. The optimal mechanism parameters for the integrated transplanting trajectory and posture were obtained. The structure design, simulation analysis and bench test of the transplanting mechanism were carried out. The results showed that the trajectory and posture of the physical prototype test and the virtual prototype simulation were basically consistent with the theoretical trajectory. When the operating speed of the transplanting mechanism was 25~45r/min, the success rate of taking seedlings was 96.1%, the success rate of planting was 91.4%, and the coefficient of variation of transplanting plant spacing was 2.31%. It can meet the requirements of vegetable transplanting operation, which verified the correctness of the proposed theoretical method and the feasibility of the mechanism.