A three-dimensional force loading device for a motor spindle is provided, and relates to the field of motor spindle testing. The device including a bottom plate; a torque loading assembly configured for testing torque performance of the motor spindle, and the torque loading assembly is in transmission connection with the motor spindle; a sleeve shell rotatably sleeved on the motor spindle, the sleeve shell is fixed along an axis direction of the motor spindle; a radial force loading assembly configured for testing radial force performance of the motor spindle, and the radial force loading assembly is fixedly connected with the sleeve shell; an axial force loading assembly configured for testing axial force performance of the motor spindle; and a intermediate force transmission mechanism connected with the sleeve shell and the axial force loading assembly.