Patterns of biomass allocation among organs in plants are important because they influence many growth processes. The Yunnan-Guizhou Plateau (YGP) is considered to be one of the most sensitive areas in China to climate changes, but we know little about how current climatic gradients on the plateau influence plant biomass allocation. Gentiana rigescens and G. rhodantha, on the YGP, are important species because they are used in traditional Chinese medicines. We therefore analyzed the biomass allocation patterns of the two species across an elevation gradient (1000-2810 m a.s.l.) on the YGP to understand and predict the impact of climate change on these plant species. We found that the total biomass, reproductive biomass, vegetative biomass, aboveground biomass, and belowground biomass in G. rigescens were all significantly larger than those in G. rhodantha (p<0.05). However, for both species the aboveground biomass was nearly isometrically related to belowground biomass, regardless of elevation, mean annual temperature (MAT) ranging from 8.4 degrees C to 18.8 degrees C, and mean annual precipitation (MAP) ranging from 681 to 1327 mm, while the reproductive biomass was allometrically related to vegetative biomass. Intriguingly, there was a significant positive relationship (p<0.05) between the slope of the allometric scaling of reproductive and vegetative biomass and elevation among G. rigescens populations, i.e. plants growing at high elevations allocate proportionately more biomass to reproduction at larger sizes and less at smaller sizes than plants growing at lower elevations. However, for G. rhodantha the reproductive allocation was negatively correlated with latitude. The results suggested different strategies in reproductive allocation in the two Gentiana plants on the YGP. Further studies are needed to investigate other environmental factors, such as nutrients and light, and genetic factors, in order to understand the trend of reproductive allometry along the environmental gradients. Our study has implications for the management and conservation practices of the two Gentiana species.