Siberian wildrye (Elymus sibiricus L.) is one of the predominant pasture species in Qinghai-Tibet plateau of China. It supplies a large number of fodders to domestic animals in spring and winter, and provides a large proportion of the summer and autumn grazing in these alpine regions. Crude protein (CP), acid detergent fiber (ADF), neutral detergent fiber (NDF) and in vitro dry matter digestibility (IVDMD) are the most important aspects of nutritive value of forages. A successful application of near infrared spectroscopy (NIRS) in combination with partial least square regression (PLSR) for the determination of four parameters (CP, ADF, NDF and IVDMD) of Siberian wildrye was developed. The standard errors of calibration (SEC, %DM) and Rcal(2) values (in parentheses) were 0.3299(0.9945), 0.7799(0.9499), 1.3430(0.9133), and 1.3762(0.9822) for CP, ADF, NDF and IVDMD equations, respectively. The standard errors of prediction (SEP, %DM) and Rval(2) values (in parentheses) were 0.3621(0.9938), 0.7878(0.9449), 1.3852(0.8907), and 1.4303(0.9790) for CP, ADF, NDF and IVDMD, respectively. A good correlation (r>0.9438) was found between results from NIRS and the traditional chemical method, and residual predictive deviation (RPD) ranged from 3.02 to 12.63. It was concluded that NIR spectroscopic technique associated with chemometrics is sufficiently sensitive to allow the accurate prediction of the concentrations of compo nents (CP, ADF and NDF) and IVDMD of Siberian wildrye.