In laser interference absolute gravimeter, the rotation of falling body leads to inaccurate gravity measurement. To reduce the influence of rotation error on gravity measurement, this article proposes a method that can measure the distance between the mass center and the optical center of falling body with high precision. Based on the torsion pendulum device, this method uses torsion wire to laterally suspend the falling body. By guiding and exciting the twisted wire, the falling body may twist around the twisted wire. The orthogonal interferometer is used to measure the displacement of the optical center of the falling body along the measuring direction in the twisting mode, and the photoelectric autocollimator is used to measure the angle signal of the falling body twisting synchronously. The genetic algorithm is used to deduct the influence of simple pendulum and torsion-frequency doubling component respectively. Secondly, an angle signal that decays with time is constructed to eliminate the influence of gas damping on the attenuation of the second harmonic amplitude. Results show that the expanded uncertainty of the offset between the optical center and the centroid in the direction of gravity is less than 0. 58 μm. The maximum angular velocity measured by NIM-3A absolute gravimeter is 24. 67 mrad / s, and the rotation error in absolute gravity measurement can be reduced to 0. 035 μGal.