Abstract: Through analysis on the agricultural requirement of gripper-type rice seedling transplanting, the fetching claw which forms D-trajectory could facilitate seedling gripping from rice box. To design a transplanter which can form a D-trajectory, the reverse kinematic model of the mechanism was established and the function of non-uniform velocity transmission ratio of the non-circular gears was solved based on the fitting technique of close pitch curve and the motion trajectory that met with the requirements of operation determined through the given typical points. Finally the pitch curve of the non-circular gears was achieved. A calculated example verified the feasibility of this reverse design method, and indicated that it was convenient to obtain more complicated motion regularity, realize trajectory reappearance and attitude controlling, which supplied a new method for the design of transplants.