The invention relates to an antenna performance detection method and system of a mobile terminal, relating to the technical field of antennas. The system comprises multiple test antennas, a phase shifter, a comprehensive measurement instrument, and a shielding box, wherein the multiple test antennas are arranged in the shielding box, the multiple test antennas are coupled with a first end of the phase shifter, a second end of the phase shifter is coupled with the comprehensive measurement instrument, and the shielding box is used for shielding an external magnetic field. According to the system, the multiple test antennas arranged in the shielding box are used for testing performance of antennas, so that the system can improve performance detection accuracy compared with the system using asingle test antenna.