A unified lattice Bhatnagar-Gross-Krook (ILBGK) model iDdQq for the incompressible Navier-Stokes equation is presented. To test its efficiency, the lid-driven cavity flow in three-dimensional space for Reynolds number Re=3200and span aspect ratio SAR=1, 2 and 3 is simulated in detail on a 48 × 48 × (48×SAR) uniform lattice using the model.The test results agree well with those in previous experiments and numerical works and show the efficiency and strong numerical stability of the proposed ILBGK model.