This paper presents a scheme for electro-optic frequency shifting. In this scheme linearly polarized light of output from CO2 laser passes through a electro-optic modula-tor and retroaction-cycle laser amplifer, under the condition of no increased harmonic components exist, the convertion efficiency of the shifting can be raised greatly. This work suggests that electro-optic frequency shifting possesses potentiality of wide appli-cation. In the experiments on checking the effect of the frequency shifting, the experi-mental device is simplifed by auto-collmating round-trip of the light beam and space delaying the modulated signal. The frequency components of the frequency shifted light is analysed by using simple method of frequency beating.