Abstract: An in-house three-dimensional unstructured-grid flow solver based on a mixing plane method was used to simulate the flow field of the compressors. Pitchwise averaging was used at the rotor/stator interface for information transport, making the unsteady problem to become a "qusi-steady" one. Thereafter the computational gird needs only one flow passage, which greatly reduced the amount of the calculation. Two different transonic compressors, NASA rotor 67 and stage 35, were tested in this paper. The overall performance maps and spanwise profiles of several aerodyamic parameters were obtained from the calculation, and the results were compared to the experiment data. The results presented here including pressure ratio, temperature ratio and adiabatic efficiency are in good agreement with the experiment data, indicating the applicability and reliability of the method.