A multi-speed and two-lane cellular automata model of traffic flow was proposed to simulate the main road traffic in city under the open boundary condi tions. By considering many real factors, the effects on traffic flow and velocit y of the main-road, produced by the bus stop and the time switched between the green light and the red light, have been analyzed. The result can reflect the re al traffic flow of the main-road in city under the control of the traffic lights .