Our objectives were to explore relationships between above-and belowground biomass and their allocation relationship with climatic factors in the grass layer in shrub ecosystems on the Tibetan Plateau. We analyzed the allocation relationship and their influencing factors on the root/shoot biomass ratio at 49 sites. The mediam values of above-and belowground biomass in the shrubland ecosystem grass layer on the Tibetan Plateau were 121.1 and 342.8 g/m² respectively, and they werehigher than that in the Tibetan grasslands. The medium value of root/shoot biomass ratio in the shrub ecosystem grass layer on the Tibetan Plateau was 3.6, which was lower than that in the Tibetan grasslands. The relationship between above-and belowground biomass can be described as a power function:y=8.0x^0.83(R²=0.48, P < 0.001). The root/shoot biomass ratio was stable with both mean annual precipitation and mean annual temperature.