A method and a device for calibrating frequency synthesizer in communication terminal are provided. The method may include: controlling the communication terminal to transmit a continuous wave signal in a specified channel; controlling a measurement device to measure the continuous wave signal to obtain a measured frequency deviation value of the frequency synthesizer in the communication terminal; calculating a center oscillation frequency point of a reference crystal oscillator of the communication terminal and a frequency calibration step corresponding to the center oscillation frequency point based on the measured frequency deviation value; and storing the center oscillation frequency point and the corresponding frequency calibration step in the communication terminal. The method can reduce frequency calibration cost and time.