In aquatic systems, bacteria are often closely linked to environmental conditions, which influence the intrasystem bacterial distribution and abundance. To investigate the response of bacterial abundance to environmental factors in lakes located in arid regions, we investigated Lake Bosten in Xinjiang Uygur Autonomous Region, China, which is the largest and most typical inland lake in this region. The inflow of the lake is supplied by melting ice, precipitation and groundwater from the mountainous regions of Tianshan, which formed a salinity gradient from freshwater to oligosaline, making it an ideal model to study the response of bacterial abundance to environmental factors in lakes. Surface water samples from 17 sites of the large-lake area (surface area ≈950 km², mean depth ≈7 m) and six sites of the small-lake area (surface area ≈300 km², depth ≈1-4 m) in Lake Bosten were collected from June 2010 to June 2011. Environmental variables of each sampling site were measured using standard methods. Additionally, the DAPI-combined epifluorescence direct counting method (DAPI-FDC) was used to investigate the bacterial abundance and their spatial and temporal distribution in the lake. The relationship between bacterial abundance and environmental parameters was then explored by the Generalized Additive Model (GAM), which is a flexible and effective technique for modelling nonlinear time-series in studies of effects of environmental factors on organisms. The average abundance of bacteria in Lake Bosten was (1.48±0.95)×10⁶ cells/mL. Generally, bacterial abundance varies from 10⁵-10⁷ cells/L from oligotrophic to hyper eutrophic lakes. Bacterial abundance in mesotrophic Bosten Lake was two times higher than the abundance in oligotrophic lakes during the same season such as Seven Rila Lake in Bulgaria, and in Shield Lake in Canada, while it was slightly lower than that in mesotrophic Lake Schhsee. In addition, the bacterial abundance in Bosten Lake was an order of magnitude lower than that of Taihu Lake and Wuliangsuhai Lake, which are eutrophic. The bacterial abundance also varied significantly with season, with the highest value being recorded in summer (2.05×10⁶ cells/mL) and the lowest in winter (3.81×10⁵ cells/mL). In the large-lake area, the maximum bacterial abundance appeared in the center during spring and winter and decreased from the center to southeast and southwest during winter; however, the opposite spatial tendency was observed during summer and autumn. The result of GAMs showed that temperature, dissolved organic carbon (DOC), chlorophyll a (Chl-a), conductivity and turbidity, explained about 81.2% of the total variation in bacterial abundance in Lake Bosten. Temperature provided the largest contribution to this variation (63.3%), followed by DOC (12.5%), Chl-a (2.7%) and conductivity (1.7%). Our data also showed that, when water temperature was ≥ 22℃, DOC was the most important variable affecting the spatial dynamics of bacterial abundance.