Dynamics of aboveground and underground biomass of Qinghai flat-stem bluegrass (Poa pratensis vayr. anceps Gaud. Cv in "＞" shape, and vertical distributions of biomass of roots, rhizomes and underground were all in "T" shape and fit equation of Y= l-βD. There was direct correlation between biomass of above ground and biomass of underground. Ration of underground to aboveground was 0.4l.