This paper explains the impact of frequency error on the performance of WCDMA mobile communication systems and what brings about the frequency error between the base station and the mobile station, and then presents automatic frequency error correction method in mobile receiver. On the basis of system requirement related to frequency stability, the integration test between the base station and the mobile station was accomplished. After applying automatic frequency error correction to mobile receiver, 4 Hz of frequency error at transmitting frequency was obtained. The result met frequency error requirement of ${pm}$0.1 ppm(about ${pm}$200 ㎐). Performance degradation due to frequency error was measured by means of Error Vector Magnitude(EVM) at transmitter and Ec/Io at receiver, respectively and then the interface requirement between Modem control signal and RF was suggested to improve the correctness of frequency error control.