Abstract:The contents of protein and fat measured by near infrared spectroscopy were researched in this paper.One hundred and twenty different brand and Specification milk powder samples were choosed.Those problems such as preprocessing of Spectrum，eliminating singular value，determining of the principal component numbers ，optimizing of wave number range were researed.The results of national standard methods were referenced.Quantitative detection models of protein and fat were established by partial least squares.The reliability of Near infrared spectroscopy mathematical model were inspected by the two ways of external inspection and interactive authentication. The unknown samples were detected by the models established in this research. Results indicated that the R2，RMSECV，RMSEP，RPD of protein calibration models were 0.952 5，0.984，0.995，4.59 respectively.The R2，RMSECV，RMSEP，RPD of fat calibration model swere 0.973 7，1.27，1.31，6.17 respectively.Both of the two models have good analytical precision. The relative errors of protein and fat measured by calibration model were Less than 1.9 % and 1.50 % respectively. The predictability of models were good.