Unsteady pressure transducers with high frequency response were used to investigate tip clearance flows in a transonic compressor rotor (ATS-2), which is a high-loading compressor with 2.2 designed pressure ratio. Static pressure contours were obtained for different operating conditions at several different speeds. It was followed that, not only an attached oblique shock emanating from the leading edge and a secondary normal shock exist in the passage at 100% speed, but also a short-range normal shock appears near the suction surface. Withclosing the outlet throttle, the shock waves move forward and finally merge into normal shock near the leading edge, meanwhile, the stage performance reaches the peak efficiency. The overall performances of ATS-2 with two different tip clearance casings were compared. It reveals that the change of casing structure and tip clearance seriously influence the performance of the compressor.