In order to ensure the precise picking of tea picking robot, the 6-DOF hybrid tea picking robot mechanism installed on the mobile vehicle was studied and designed. According to the topological structure design theory of robot mechanism based on orientation feature, a 6-DOF hybrid manipulator was proposed and designed. The correctness of the mechanism was confirmed by analyzing the position of the forward and inverse solutions of the hybrid mechanism. Taking the minimum sum of lengths of links as objective function, the nonlinear programming method was used to optimize the dimensions of the links of the mechanism, and the optimal dimensions of all the links were obtained. The mass parameters and position parameters of the counterweight under complete balance were obtained by using the finite position method, so that the swing was constant to 0 and the position of the total center of mass of the mechanism was constant. The genetic algorithm was used to study the partial balance optimization of the swing force, and the optimal solution of its counterweight mass and position parameters was obtained, and the minimum total swing force was obtained within a certain range. The partial balance optimization results showed that the fluctuation of the centroid trajectory in the y and z-directions was decreased by 53.72% and 25.10%, respectively, and the total swing force fluctuation was decreased by 43.33%, which verified the effectiveness of the partial balance optimization. Based on the finite position method, the steps of action balance analysis laid a technical foundation for the structural design and prototype development of the hybrid tea picking robot. 