Under the condition of non-paraxial approximation, a formula of the relationship between the cavity size, mirror curvature, deflection angle and the space position of self-reproduction resonant laser in the laser gyro experiment is derived by using geometric optics theory. The difference between the formula and the matrix optical results under the usual paraxial approximation is compared. The effect of adjusting the mirror deflection angle on the effective cavity length, optical path area, gyro scale factor and laser output position is discussed, which has guiding significance for the adjustment of resonator in laser gyro experiment.