The invention relates to the technical field of automobile safety, and especially relates to a tire pressure monitoring system. The system comprises a controller, a low frequency trigger and a tire pressure sensor, the controller outputs a control command to the low frequency trigger, the low frequency trigger generates a low frequency signal to trigger the tire pressure sensor, the tire pressure sensor acquires tire pressure information and outputs the tire pressure information to the controller, the low frequency trigger comprises, sequentially serially connected, a resistor R, a capacitor C and an inductor L, the suspension end of the resistor R is connected with a power supply through a first electronic switch and is grounded through a second electronic switch, and the suspension end of the inductor L is connected with the power supply through a third electronic switch and is grounded through a fourth electronic switch; and the controller outputs a control command to control the opening or closure of the first, second, third and fourth electronic switches. The invention also discloses a control method of the system. The system and the method improve the trigger ability of the low frequency trigger, and guarantees that the tire pressure sensor rotating with a tire to any position can be triggered by the low frequency trigger.