In order to explore the flow characteristics at tip clearance and the coupling deformation of the blade during running on the centrifugal air compressor,based on the fluid-structure coupling heat transfer theory,the hydrodynamic and structural mechanics numerical calculation models of the impeller were established.Considering centrifugal force,aerodynamic force and thermal stress,the stress and deformation distribution at the blade tip under different tip clearances were analyzed.The results show that tip clearance can generate inlet separation vortex and tip leakage flow,which together disturb the flow in the main flow zone and increase the flow loss.Under the combined action of centrifugal force，air pressure load and thermal load，the maximum deformation of the blade occurs at about 0.3 chord length of the blade tip.The maximum deformation of the suction surface is 3.7% larger than that of the pressure surface.With the decrease of the blade height,the deformation decreases gradually.The stress value at the leading edge of blade tip is small,and the maximum stress value at the pressure surface and suction surface is not in the same axial position.With the increase of clearance value，the overall stress value at the top gradually decreases.Through the flow field and structure analysis，the optimum clearance size was determined，and the blade was optimized.The aerodynamic performance and safety of the blade were significantly improved after optimization.