To improve the consistency and flexibility of master manipulator in minimally invasive surgery, an 8-joint series force feedback master manipulator was designed. From the perspective of position-posture decoupling, this design realized position-posture decoupling through a double parallelogram structure, which improved the consistency of operation in different positions and postures. Using the modified D-H parameter method and inverse transformation method, the forward and inverse kinematics of the master manipulator were solved respectively, and the position-posture decoupling strategy was verified from the perspective of kinematics. Based on Monte Carlo method, the minimum working space of the master manipulator was analyzed by MATLAB programming. Then the Jacobi matrix of the master manipulator was solved. Based on the global conditioning index and global conditioning mean square error index, the comprehensive motion performance index of the master manipulator was defined. Taking the minimum working space as a constraint, the motion performance and structure size of the master manipulator were analyzed and optimized through genetic algorithm. The optimization results show that, compared with the initial design, the comprehensive performance index of the master manipulator is improved by 15.32%, and especially the workspace volume with good motion performance is increased to 3 times of the original, which basically includes the operation required work area. On the basis of ensuring the consistency of operation and enough working space, the master manipulator has good and stable motion performance.