Abstract:This article reports research results on the characteristics of biomass, net primary productivity and conversion efficiency of solar radiation in Tianzhu alpine Rhododendron + Salix-moss grassland (RMG), Polygonum viviparum grassland (PVG), Kobresia capillifolia grassland (KCG)and improved grass-forb semiartificial grassland, perennial grass artificial grassland and oat grassland. The aboveground and underground maximum biomass of RMG and PVG on the northern slope are larger. The maximum aboveground biomass and standing crop in the improved grasslands have been increased by irrigation, fertilization, ploughing and seeding, while the underground biomass has been decreased. Among the natural grasslands, the net primary productivity of the aboveground, underground and whole community (above underground part) of PVG are the highest, and that of RMG the lowest. The net primary productivity of the aboveground of the three types of improved grasslands are markedly higher than their original grassland-KCG and increases with the intensity of improvement, but that of underground is markedly lower and decreases with the intensity of improvement. The conversion efficiencies of total radiation for aboveground in RMG, PVG and KCG are 0.074%, 0.155% and 0.110%,respectively. The conversion efficiencies for aboveground of the three types of improved grasslands are higher than that of natural grassland with the exception of underground. The conversion efficiency for the whole community in oat grassland is higher than that of natural grassland.