The arid and semi-arid area in Northwest China is an important dust source region in the world. Compared with other major dust sources around the globe, this region is characterized by the complexity of its surrounding landform. In this paper, the WRF mesoscale weather forecast model coupled with the GOCART atmospheric chemical-aerosol radiation and transmission model was used to simulate a large-scale dust episode which originated from the dust source region in northwest China from April 27, 2011 to May 2, and verified by the MODIS remote sensing data, the airborne dust reservoir effect of Tarim Basin on dust aerosol distribution was found. In order to verify this effect and its impact on the air quality of downwind city, hourly mass concentration of water-soluble Ca²⁺ in PM₁₀ was monitored in Lanzhou during this period. Combined with CALIPSO vertical aerosol feature mask product and HYSPLIT air mass trajectory model, PSCF was used to analyze the 48-hour backward trajectories of air mass which arrived at Lanzhou during this dust episode. The simulation, remote sensing and site monitoring indicated that the effect of Airborne Dust Reservoir would constrain and accumulate the inbound dust aerosol. Meanwhile, if the wind direction changed, the suspended dust aerosol constrained by the basin could re-release as a secondary dust source, which would exacerbate the impact of the dust episode on the air quality of downwind city.