Summary: A hybrid control model of traffic flow is established based on the continuous Petri net, and the traffic signal actuated control at an isolated intersection is studied by analyzing the discretized hybrid Petri net model of traffic signal control. Based on the analysis of parameters of the hybrid Petri net model, the calculation method of the total vehicle residence time is presented. According to the complex relationship between the marking of places and the enable degree of transitions, the marking change law of places is studied. By taking the minimal average vehicle residence time as the objective, a mathematical model for the optimization of actuated control is established and a simulation is carried out to calculate the green time of each phase. The calculation result indicates that the average delay of four phases is shortened significantly and that the traffic signal actuated control at the isolated intersection is better realized by using the optimization method based on the hybrid Petri net.