A GPS module test system for automatically calibrating a test signal includes a GPS test fixture, a satellite signal simulator, and a computer. The GPS test fixture carries a GPS module under test and is electrically connected to the same through contact, so as to receive a digital signal generated by the GPS module after the test. The computer receives device information of the GPS module under test through the GPS test fixture, and controls the satellite signal simulator through a GPS signal sample database, so as to generate a GPS analog signal to test the GPS module under test. Thereafter, on receiving the digital signal generated by the GPS module under test and determining the received digital signal is attenuated, the computer automatically gains a transmitted test parameter, so as to transmit the GPS analog signal in a preferable state.