Abstract: Path length control configuration for ring laser gyroscopes (RLGs) maintains the stability of frequency of beams through controlling the path length, which is very important to improve the performance of RLG. Aiming at the deflection of beams in working RLG caused by the distorted control mirror in traditional path length control configuration, which leads to dispersion and changes of loss to affect the performance and precision of RLG, the path length control configuration for RLG was researched and a new path length control configuration which could reduce the effects of distorted control mirror on RLG was designed. Moreover, the simulation and optimization on the new path length control configuration were done with the direct coupled field analysis of the finite element (FE) method. Results show that the new path length control configuration reduces the distortion of the control mirror, improves the performance and precision of RLG, the zero-bias stability is increased from 0.7/h to 0.3/h.