Abstract: In order to eliminate the interference of coexisting ingredients in the absorption spectra of norgestrel compound tablets without any preliminary separation, an orthogonal function spectrophotometry was introduced. The coefficient of quadratic polynomial for ethiny estradiol was measured with 751 G spectrophotometer over the wavelength range of 284 nm to 305 nm at 2-nm intervals using six—point orthogonal polynomials. The coefficient of linear polynomials for norgestrel was calculated over the wavelength range of 241nm—265nm at 5-nm intervals using six-point orthogonal polynomial. The recovery for ethiny estradiol was found to be 101.4±0.7％, and for norgestrel 99.60±1.75%.