Abstract: This paper studies the determination of optimal single cycle of intersection of urban road in real time .The derivation of the shortest signal cycle and the best signal cycle were analyzed .Four models of signal cycle time were deter-mined .In order to choose the optimal signal cycle ,the paper adopted the delay ,the largest queue length ,the average number of stops and capacity for the comprehensive evaluation ,which can overcome the limitation of less evaluation pa-rameters .During the evaluation ,the dimensional ranges of different parameters were standardized ,and the weight coeffi-cients of different parameters were determined .Finally ,the optimization model was verified based on the actual data and Matlab program .The results show that a single index leads to different signal cycle time ,while the other indicators can not be ideal .The comprehensive evaluation model can directly determine the optimal signal cycle time and ensure that the four evaluation parameters are optimal .