The invention discloses a traffic light control method and system, and the method comprises the steps: burying a traffic flow collection sensor (1) under each traffic intersection; integrating a GSM module (2) and a control module (3) in a small case; transmitting traffic flow information of a stop to a next intersection in a manner of short messages through the GSM module (2), and enabling the control module (3) of the next intersection to carry out the conversion of the relation of traffic flow and passing time after the transmitted traffic flow information is received, so as to write a control program; controlling the switching of the traffic lights of the intersection, and displaying the duration of lights with the corresponding color. The system is simple in structure, is low in cost, can be installed at each intersection easily, and is high in practicality. The system employs a one-station communication mode, avoids a big project of a main station server. Each intersection communicates with the adjacent front and back intersections. The system is high in practicality, and the mutual relation is close and independent.