The traditional dual frequency laser with controllable frequency difference was based on birefringence effect.By studying phase characteristics of the S-polarized and P-polarized light in total internal reflection and antireflection films,a dual frequency laser with controllable frequency difference based on dual total internal reflection and tilted antireflective film is proposed.Frequency difference is controlled by adjusting the incident angle or designing the structure of antireflective film.Finally,the experimental results show that a hard sealing transmission window of helium-neon laser has large uncontrolled but stable thermal residual stress birefringence.Dual frequency laser with medium frequency can be made by this method.