Net Primary Productivity in desert-oasis region in Northwest China is estimated combined the model of light energy utilization with EOS/MODIS data from May to Oct.. On the basis of NPP and observed value of aboveground biomass, biomass model is also built, then, temporal and spatial distribution of biomass and NPP are analyzed. The results show that NPP is larger in June and July than other growth periods, grass LAI and NPP change rapidly from May to June. Estimated error of 44 cases by the biomass model is less than 20%, which show that the biomass model is very good , the model can describe growing status. Photosynthesis and respiration are different because of different type grass , three types grass are more adaptive to desert environment and the biomass are also big, the grass types include Alhagi sparsifolia, Lycium ruthenicum and Reaumuria songarica. The grass biomass is influenced by many factors such as grass type, total cover and plant height et al.