Backscattering characteristics of mirror laser gyros and total reflection prism laser gyros are studied based on their structure features. The functional relationship between the refractive index inhomogeneity and backscattering is analyzed theoretically. The methods and formulas to calculate backscattering coefficients of the two kinds of laser gyros are deduced according to the multi-layer high reflection film structure of the mirror laser gyro and the total reflection characteristic of the total reflection prism laser gyro. The correctness of the proposed method is verified by the comparison of numerical simulation and experimental results. The result shows that the non-uniform loss is the primary factor to influence the locking area of laser gyros and the refractive index inhomogeneity is the secondary factor.