Abstract: In order to satisfy the high precision, high stiffness and high load bearing requirements of the six-axis force sensor for industrial robots, a partial decoupling design idea is presented. A heavy load Stewart six-axis force sensor is synthetically optimized based on both the accuracy and the stiffness. Firstly, a set of optimal parameters are obtained by the structural parameter optimization. Secondly, the influence of coupling factors on the output characteristics of each branch is analyzed, combining with the experimental data of the spherical hinge prototype and the prototype without decoupling. Thirdly, the sensor is designed by partial decoupling and verified by finite element simulation. Finally, the prototype experiment results demonstrate that the designed partial decoupled six-axis force sensor shows a significantly raised stiffness besides a high precision compared with the traditional Stewart six-axis force sensor, which satisfies the design requirements.