Frequency test system of RF transmitter and method thereof

The present invention provides a test system of wireless communication device and method thereof. The method includes steps of first issuing a high-frequency signal when a wireless communication device to be tested is positioned under a transmitting state; attenuating the high-frequency signal with an attenuator; mixing the attenuated signal through a mixer and a standard frequency generated by a phase-lock loop frequency synthesizer to obtain a mixed signal; filtering the mixed signal to be a low-frequency signal by passing it through a low-pass filter; amplifying the low-frequency signal with an amplifier; converting the amplified signal into a waveform signal through a trigger; outputting the waveform signal to a single-chip microcomputer to calculate a waveform frequency; and dividing the waveform frequency by the standard frequency to obtain a frequency error value issued by the wireless communication device.