Abstract: The mathematical statistics method is adopted to describe the characteristics of traffic flow: law of vehicle arrival, traffic composition and the response time of stop and start. A special signal intersection of Beijing is taken as an example for investigation, where the vehicle arrival and its distribution law are counted and analyzed. The investigated results show that the vehicle arrival at the intersection is consistent to poisson distribution. The authors also introduce how the stomchastic numbers are produced and how the numbers are applied in simulation, and moreover compare two randomizers. The results show that the random numbers generated from prime number modularity randomizer have better homogeneity.