Abstract:Background and Aims Vegetation transect is an effective method to study the relationship between global change and terrestrial ecosystem. However there are few researches on biomass gradient characters of grassland vegetation and their environmental driving mechanism. The transect measurement was used in this study to analyze biomass gradient change of grassland vegetation in Inner Mongolia. The following questions were tried to answer: (a) How does grassland biomass change along with longitude and latitude as well as water and thermal gradients? (b) Which climate factors will produce pivotal effect to grassland biomass change? (c) How do climate factors control material production process of grassland ecosystem? Methods The selection of 49 sample sites was principally defined by a 1 900 km long×150 km wide transect across the grasslands of Inner Mongolia. Aboveground and belowground biomasses were measured in the sample sites. The correlativity between biomass and climate factors was analyzed using China climate grid database which constructed by Chinese Ecosystem Research Network. Key results Grassland biomass was found to be negatively correlated to mean annual temperature, ≥0 ℃ accumulated temperature, ≥10 ℃ accumulated temperature and annual hours of sunshine. Contrarily it was positively correlated with mean annual precipitation and mean annual relative humidity. Among climate factors, mean annual temperature and mean annual relative humidity effected grassland biomass the most obvious. Conclusions Aboveground and belowground biomasses present visible change regulation along with longitude and latitude as well as climate gradients. Mean annual precipitation was shown as a key role to grassland biomass although its effect ways were complicated. The study suggested combined and integrated relationships of environment factors should be considered in researches of biomass forming and changing.