The sources of cavity stress in total reflection prisms laser gyro are complex, and strong stress may seriously affect the gyro′s accuracy. Based on the prism material dielectric constant change under stress, the effect of stress-birefringence on the gyro output is analyzed systematically by using Jones matrix and the elastic-optic effect theory. The energy distributions of the reflected and transmitted light are obtained at Brewster angle, and the explanation of the reflected interference speckle is given. The reflected light intensity is simulated corresponding to uniform gradient, point concentration and complex stresses fields between the prism and cavity. The related experimental results agree with the simulation. An engineered equipment for prism and other correlates stress detection is designed.