Abstract: Based on three-dimensional computational fluid dynamics method,the flow fields of two opposite impeller blade tip clearance distribution compressor stages with vaneless diffuser were analyzed.The law and action mechanism of tip clearance distribution effect on the high charging ratio transonic centrifugal compressor impeller and vaneless diffuser performance were researched.This proves that non-uniform chord direction blade tip clearance distribution impellers have wider operating range.The pressure ratio and efficiency of compressor stage whose outlet axial clearance height is smaller than inlet radial clearance height are higher than that of compressor stage whose outlet axial clearance height is larger than inlet radial clearance height.The smaller outlet axial clearance height weakens the clearance flow in aft half of impeller passage,improves the impeller aft passage power input and obtains higher impeller pressure ratio and compressor stage pressure ratio.The smaller outlet axial clearance height gets higher efficiency since it reduces impeller aft blade tip clearance leakage vortices intensity and makes the vortices breakdown and dissipation loss less in impeller passage and vaneless diffuser passage.