Based on the theory of matrix optics,temperature effect of Ring Laser with the Total Reflection Prisms (TRPRL) is studied. A 3×3 transformation matrix of optic system with the variation of refractive index is investigated theoretically. A deflection model of ray in resonator for the variation of refractive index is established. The regular pattern of deflection in the TRPRL caused by temperature shift is discussed. The method of reducing the influence of temperature effect is studied. These conclusions have important purposes in design and application of the TRPRL.