In many cases,the scattering can be an overpowering contributor to the spectrum,sometimes accounting for most of the variance in the data.Although the degree of scattering is dependent on the wavelength of the light that is used and the particle size and refractive index of the sample,the scattering is not uniform throughout the spectrum.In order to remove the effects of scattering and noise on multivariate calibration of IR spectral signals,orthogonal signal correction (OSC) was used as a method to preprocess the infrared spectra of the hydrocarbon source rocks to be quantitatively determined,thus to establish the calibration model of hydrocarbon source rocks before and after pretreatment by inetval partial least square (iPLS).Pretreatment was smoother and more orderly array.This indicated that the major information in hydrocarbon source rocks spectra could be reserved while part of noise was removed by OSC method.In this study,pretreatment calibration model was obtained,the model’s correlation coefficient is 0.994 04 and RMSE is 0.635 2,but with no pretreatment the calibration model’s correlation coefficient is 0.770 9 and RMSE is 3.925 7.