Abstract: When a vector optical field acts on the metasurface-based diffractive light sail, the maximum acceleration, self-stabilizing thrust, and attitude controllability of the diffractive light sail can be enhanced. In a vacuum environment, it is important to measure the optical force acting on the diffraction light sail to establish a comprehensive space dynamics model under the influence of vector optical fields. Based on the weak force measurement technique, we have designed an optical force measurement torsion pendulum for both regular and irregular shaped diffraction light sails. The measurement accuracy of regular-shaped light sails can be enhanced by ensuring that the size of the torsion pendulum and relative position errors of each component are strictly controlled. The force measurement has a relative error of 0.55‰. We have also designed a torsion pendulum to measure the optical force of the irregular-shaped light sails, which can hardly calculate the moment of inertia. There are two standard spheres on the torsion pendulum that can be placed or removed at any time. The magnitude of the optical force acting on the complex object can be measured by calculating the moment of inertia of the spheres. This research enhances the efficiency and flexibility of optical force measurement experiments, providing data support for applications such as laser-driven light sail and space debris remediation.