In order to reveal the impact of the bow shock of downstream rotor on the tip leakage flow of upstream rotor in a counter-rotating compressor, the unsteady numerical simulation of a counter-rotating compressor was conducted with tip clearance of 0.2, 0.5 and 0.8 mm of the upstream rotor, respectively. Results showed that impacted by the sweep of the downstream rotor bow shock, a weak compression wave was formed on the pressure surface near the tail edge of the upstream rotor, which could be weakened gradually with the increase of the leakage flow of the upstream rotor. On the suction surface near the trailing edge of the upstream rotor, a strong compression wave perpendicular to the tangential direction of the blade profile was formed causing the downstream rotor bow shock, and its position was basically not affected by the sizes of tip clearance. Also, the pressure difference between the suction and the pressure surfaces near the tail edge of the upstream rotor increased by the bow shock, which led to the augment of the tip leakage flow, and then the flow loss. With the increase of tip clearance, the motivator of the main frequency of the pressure fluctuation, which was located among the blade tip half-chord region belonging to the leading edge of the upstream rotor, was changed from the channel shock to the tip leakage flow and the main frequency decreased gradually. While the blade tip half-chord region was located at the trailing edge, the pressure fluctuation was mainly dominated by the downstream rotor bow shock, and its main frequency was consistent with the bow shock sweeping.