AbstractSiberian 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 R2cal values (in parentheses) were 0.329　9(0.994　5),0.779　9(0.949　9),1.343　0(0.913　3),and 1.376　2(0.982　2) for CP,ADF,NDF and IVDMD equations,respectively.The standard errors of prediction (SEP,%DM) and R2val values (in parentheses) were 0.362　1(0.993　8),0.787　8(0.944　9),1.385　2(0.890　7),and 1.430　3(0.979　0) for CP,ADF,NDF and IVDMD,respectively.A good correlation (r>0.943　8) 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 components (CP,ADF and NDF) and IVDMD of Siberian wildrye.