The direct calculation models of spectral transmittance of single and double slabs consisted of semitransparent solid materials were developed based on ray trace method,and a new inversion method of optical constants ( k is extinction coefficient and n is refractive index) of materials was proposed based on transmittance spectrograms of double slabs. Differences between the new method and two others currently used methods were studied,and application range of methods was also investigated. Optical constants of selenide glass attained in references were selected as true values,and spectral transmittances of glass simulated based on direct calculation model were regarded as experimental values. Optical constants of selenide glass were achieved by inverse models. Influences of measurement error on inverse results were also determined. The results showed that: (1) based on transmittance spectrograms of double slabs in which thickness of single slab is the same,the new proposed method can attain optical constants of materials; (2) the effect of optical constants n and k on three inversion methods are urgent larger,but inversed calculation precision of optical constants are higher in most application ranges; (3) the influence of measurement errors existed in experimental datum on the inverse precision of three methods are urgent distinctness The direct calculation models of spectral transmittance of single and double slabs consisted of semitransparent solid materials were developed based on ray trace method, and a new inversion method of optical constants (k extinction coefficient and n is refractive index) of materials was proposed based on transmittance spectra of double slabs. Differences between the new method and two others currently used methods were studied, and application range of methods was also investigated. Optical constants of selenide glass attained in references were selected as true values, and spectral transmittances of glass simulated based On const calculation of selenide glass were achieved by inverse models. Influences of measurement error on inverse results were also determined. The results showed that: (1) based on transmittance spectrograms of double slabs in which thickness of single slab is the same, the new proposed method can a ting optical constants of materials; (2) the effect of optical constants n and k on three inversion methods are urgent larger, but inversed calculation precision of optical constants are higher in most application ranges; (3) the influence of measurement errors existed in experimental datum on the inverse precision of three methods are urgent distinctness