Abstract: Desert zones, accounted for approx. 18.5% of the total land area, was the important component of the land ecosystem. Desert ecosystem was characterized by low biodiversity and low stability, so it was easily disturbed by external forces, and it was difficult to recover. The structure and species composition of a community were the result of community succession, and they were closely relevant to the stability of ecosystem. Biomass was an important carrier of material cycle (carbon cycle) of ecosystem, it was an expression of the productivity, also was a key index evaluating the structure and function of ecosystem. Thus, the study on biomass in desert areas was very important for understanding the productivity and capacity of desert ecosystems. In this study, three types of widely distributed plant communities in Gurbantunggut Desert, Northwestern China were chosen: 36 Ephedra distachya communities, 28 Seriphidium terrae-albae communities and 13 Artemisia songarica communities. Vegetation investigation was conducted two times (seasons) in early summer and early autumn, respectively, to get the data of species composition and species richness. Then the standing aboveground biomass of herbs was gained by cutting at the ground level, and the biomass of shrubs by estimating models. The aims were to explore the seasonal changes in species composition and species richness, and to compare the aboveground biomass of different life-forms and to understand the relationship between biomass and richness of herbs in different seasons. The numbers of families and species in E. distachya and S. terrae-albae communities were more than those in A. songarica communities in early summer, whereas the numbers reduced greatly in all the three communities in early autumn. There were five life-forms in summer, and the ephemeral plant had most species. In autumn, the ephemeral and ephemeroid plants disappeared, and there were only three life-forms left, and the annual plant had most species at this time. The richness value of each community types in summer was more than that in autumn. Species richness of A. songarica communities in summer was significantly higher than those of E. distachya and S. terrae-albae communities; while in autumn, there was no difference between the three community types. In each community types, species richness in summer was positively correlated with that in autumn, indicating the structural stability of desert communities. The aboveground biomass of herbs (0.67-6.99 g/m²) was slightly more than that (0.89-4.2 g/m²) in autumn. The total aboveground biomasses of three types of communities were 73.19, 85.38 and 54.21 g/m², respectively; and the three constructive species accounted for 86.03%, 84.07% and 89.65%, respectively; while the percentages of herbs were all less than 5%. There were “Single-hump Type” relationships between herbaceous richness and their aboveground biomass both in summer and autumn, indicating highest richness at middle biomass. Although herbaceous biomasses were lower, the time crisscross of short vegetated and long vegetated plants showed an important ecological significance in maintaining biodiversity and surface stability of desert ecosystem. Totally, compared with other deserts in similar latitude in China, the three desert communities in Gurbantunggut Desert had the characteristics of obviously seasonal changes in species composition and richness, but low biomass.