Two hundred samples of Pennisetum purpureum, dried and ground at 1 mm particle size, from a wide range of varieties, physico-chemical characteristics and origin, were used to obtain the equations of calibration and determine the chemical composition of this species through the technique of NIRS. The algorithm to obtain the equations of calibration of each of the indicators used the data bank from the laboratory analyses and the values of wave length from the readings of the samples in the near red reflectance spectrophotometer through crossed validation. The equations of calibration for the DM, CP, NDF, ADF, cellulose, hemicelluloses, lignin, ashes, and in vitro digestibility of DM of the P purpureum were appropriate, not only for having a low standard error of calibration, but also for the high coefficient of determination. it is recommended to use the NIRS to determine the chemical composition of any variety of this species, having the necessary equations of calibration.