Abstract: The secondary flow loss plays a main part in the total loss of high pressure turbine's(HPT).Based on the structure of one type aero-engine,this paper is focused on mechanic of the tip clearance structure,which influences the turbine characteristics.Numerical results agree well with the experiment data.The detailed information of the flow fields shows that,with the same tip clearance flow area,the step and shrink tip clearance shape perform better than line tip clearance shape,while the groove and bulge shape is worse relatively.Suppressed by the up passage vortex at upstream side of blade,the intensity and scale of the tip clearance leakage vortex is decreased.There are flow separations at the front blade of bulge tip clearance.The high speed area of groove tip clearance increases the secondary flow loss dramatically.