For the micro torsion bar used in inertial navigation, the torsional stiffness should be evaluated precisely. A computer-controlled instrument for stiffness measurement based on static measuring principle was introduced for variant section micro bars, The main hardware of the system includes a precision motorized rotary stage and a torsion sensor. The stepping resolution of angular displacement is 0.00250, the measurement accuracy of moment is 0.05mN•m. The measurement software was programmed on the LabVIEW platform for virtual instrument. The measuring experiments indicate the device can be used for automatic testing of stiffness of the torsion bars with high accuracy and efficiency.