Considering the birefringence and super twisted effect of the super twisted nematic liquid crystal，the effect of oblique incidence on output characteristics of super twisted nematic liquid crystal filter was studied.The theory of super twisted nematic liquid crystal filter was analyzed，and the transmittance expression was derived according to optical theory.The further experiments verify that the transmittance is associated with incident angle，and has nothing to do with the direction of oblique incidence.With the increase of oblique incident angle，the transmittance peak of super twisted nematic liquid crystal filter shifts to short wavelength.