In the static interferometer system, the variable refractive crystalLiNbO3 with electro-optic modulation was used in static Fourier transforminterferometer, where both sides load phase opposite modulation signal separatelyso to raise the spectrum resolution in the same size of the instrument by theincrement of optical path difference. According to the derivation of the opticalpath difference function with refraction modulation, the maximum optical pathdifference was calculated and the spectrum resolution was analyzed to be 16.7times previous one when the refraction modulation was 0.030 in the same size ofinterferometer. The simulation result indicated that the refractive modulationwould be reduced when the wavelength increased, and the value of optical pathdifference will be bigger when the x′ increased. In actual detection process,because spectral region 500-1 100 nm is relatively narrow, the spectrumdistortion by the wavelength change is not big and may be compensated through thedemarcation. This method can increase the optical path difference withoutmechanical scanning, and possibly raises spectrum resolution of the staticinterferometer.-optic modulation; Spectrum resolution