The aboveground biomass and spatial distribution of shrubs were obtained by analysing the data of 7 groundwater observation wells and 19 vegetation plots in the lower reaches of the Tarim River in 2004. It was found that the respective biomass of Tamarix ramosissima and T. hispida all presented a unimodal pattern of decreasing before increasing: Longitudinally, the aboveground biomass account for 70% of all within the scope of 0～200m by comparing the distribution of 0～200m and 200～400m apart from the river course; Transversely, the maximum appeared at the plot of 450m distance from the river course. As a whole, the different adaptability to environmental heterogeneity of T. ramosissima and T. hispida, resulted from the difference of physiological and ecological characteristics, led to the distribution of their own. T. ramosissima distributed widely in the lower reaches of Tarim River due to its eurytopicity, however, T. hispida appeared only at a few sections for its high requirement to moisture and salinity conditions. Groundwater depth was the main factor that influenced the change of the shrub biomass. When groundwater depth was less than 5m, T. grew well, however, it would be coerced seriously when the groundwater depth was more than 6m. The shallow water content of soil was meaningless to water utilization of plants, in addition, salinity is not the primary intimidator in this region because of having unique mechanism to adaptive and resistant the salinity.The aim of this paper was to provide theoretical bases for the restoration and protection of vegetation in the arid and semi-arid region by studying the spatial distribution and influencing factors of shrub biomass.