The force vector of the key equipment for many important applications during impacting and adjusting is necessary to be considered, which may affect the control precision and the system structure design. The force vector measurement is the confirming of the magnitude, direction and the action point, which could be transformed the measurements of the three forces and torques according to the force equivalent principle. According to the characteristics of the piezoelectric force sensor, the expression of solving the three component forces and the coordinates of action point are deduced based on the equation of static equilibrium. The reasonable number of the sensors is confirmed and the mathematical model of solving the force vector is built. Experiments show that the measurement system satisfies the requirements of the motor force vector test according to the model.