Abstract: The accumulation dynamics of aboveground biomass of second year Poa pratensis var. anceps Gaud. cv. Qinghai was studied to understand the regulation of aboveground biomass accumulation in Alpine Regions of Qinghai province. The accumulation of stem (S), leaf (L), ear (E) and above ground biomass (Ba) of Poa all fitted to monofactorial cubic equations:S∧=21.04-2.12 d+0.10 d²-0.00062 d³,L∧=2.71+0.55 d+0.031 d²-0.00022 d³,E∧=3.17-1.27 d+0.070 d²-0.00051 d³,B∧a=26.92-2.84 d+0.20 d²-0.014 d³ respectively. From greening up to mid May, the Poa are in a nutritional growth period with tiller number, leaf area, and leaf number increasing rapidly. Mid May to mid June, the speed of above ground biomass accumulation of the Poa reached a climax with the highest stem, leaf, ear and above ground biomass of 6.836, 2.611, 2.409 and 11.876 g/(m²·d) respectively, and a stem/leaf ratio of 1∶1.61. Stem, leaf and above ground biomass of the Poa reached the maxima of 220.3, 151.7 and 406.1 g/m² respectively in mid July while ear accumulation reached a maximum of 92.3 g/m² in mid June. The relationship between total aboveground biomass (Ba) and plant height (H), leaf areas (LA), and stem number (N_T) can be represented by the equation B∧a=-4.44+6.44 H-58.88 LA-0.065 N_T+0.029 N_L, Plant height had the greatest direct effect on aboveground biomass accumulation while LA, NT, NL influenced aboveground biomass accumulation indirectly by affecting H.