Abstract: For the study of error factors in four frequency differential laser gyro, the radiation trapping effects need to be considered. From the physics mechanism of laser radiation trapping effects, the s coefficient was introduced to represent the burning holes were partly filled in, and the new correction formulas are derived from the self-consistency equations, which can solve the contradiction between the Aronowitz’s method and the experiment results. Then, based on the four lasers mode, the fine mode coupling effects were considered from the physics mechanism of atom transition. Finally, the radiation trapping effects correction formulas of four frequency differential laser gyro are obtained in the case of two isotopes, which can be helpful to the theoretical research on four frequency differential laser gyro.