In order to increase the workspace and carrying capacity of a robot shoulder joint and to improve its popularity and adaptability, a novel robot shoulder joint was proposed based on 3-RRR orthogonal spherical parallel mechanism. The statics performance of the robot shoulder joint was analyzed and the structure parameters were designed. Firstly, the static transmission equation of the robot shoulder joint was established based on the principle of virtual works.Then,by use of the norm in matrix theory, the force Jacobian matrix was introduced into the statics performance evaluation index to define the statics performance evaluation index and the global torque performance evaluation index and to plot the performance atlas of the statics performance evaluation index at the work spaces of the robot shoulder joint. Furthermore, the objective optimal function based on the global torque performance evaluation index of the robot shoulder joint was established, and the relation of the objective optimal function and the global torque performance evaluation index was analyzed. By use of fully automatic searching method, the optimal structural parameter ranges of the robot shoulder joint are 49.8-60 mm for the middle follower length of WB and 90-112 mm for the frame connecting rod length of AU. Analysis results show that the robot shoulder joint has good static transmission performance at the initial position, and the static transmission performance decreases with increasing turning angle. Finally, using a set of optimal structural size parameters, a novel robot shoulder joint was designed.