Qinghai Province is one of five largest pasturing areas and ranks four th in China. It is of great importance to learn the growth status of grass in t ime to ecoenvironment protection and sustainable development of stock raising. Based on the data of fresh grass weight per square meter from 22 ecoenvironmen tal monitoring stations (which were established by Qinghai Meteorological Bureau in 2002) during grass growing season from 2003 to 2004, as well as the same p eriod of MODIS data, by preprocessing，cloud detecting, EVI computing and monthl y maximum EVI compositing, MODIS EVI data were obtained corresponding to grass output data. The relationship between grassland output and EVI was established a ccording to the grass growing season and grassland type. The results show that g rassland output have a good correlation with MODIS EVI, and it can be better des cribed by the exponential function. Furthermore, the grassland output model base d on the grass growing season is better than that of based on grassland type.