Abstract:The differentiation of plant height is the result of longterm adaptability of plants to environment. It is helpful to understand the diversity of germplasm resources by studying the response of plant phenotype and biomass distribution to plant size. Based on the research materials of wild Bromus inermis, we studied 8 phenotypic traits and biomass of 3 species of small, medium and large plants, and investigated the effect of plant height difference on phenotype and biomass distribution by ANOVA, coefficient of variation and linear regression model. The results show: (1) with the increase of plant height, the number of tillers decreased by 46.7%, stem diameter, number of stem nodes, panicle length and spikelet length were the opposite, and the variation of tiller number among these phenotypic traits was the greatest can reach 106.32%. (2) There was no significant relationship between the biomass variation of each component and plant height. The small plants put more biomass into leaf and underground organs, medium and large plants put into panicle and stem organs. There is a linear growth relationship between aboveground and underground biomass. (3) In addition to spikelet width and root length, other phenotypic traits, panicle biomass and aboveground biomass have sizedependent effects (P<0.05).