The capacity is impacted badly by pedestrians’ violation behavior at signal intersections. In order to quantify the impact,the time-headway and the vehicular speed from start-up to reach the stable saturation flow with and without pedestrian traffic are used as the direct measurements. Using the statistical analysis,the timeheadway of saturation flow is mainly affected by the position of pedestrians and the degree of pedestrians ’influence is classified into four levels. Then the speed-time profile for the vehicular acceleration at each level is fitted by Curve Fitting Software. Based on the effect to the time-headway and acceleration time,the model of capacity influenced by pedestrians is established and the influence is quantified, which enriches the fundamental theory of traffic engineering. The result shows that the vehicular capacity can be decreased by 14%at the worst case( level I). The conclusions obtained in this paper are valuable for better management of the signal intersection. The capacity is impacted badly by pedestrians’ violation behavior at signal intersections. In order to quantify the impact, the time-headway and the vehicular speed from start-up to reach the stable saturation flow with and without pedestrian traffic are used as the direct measurements Using the statistical analysis, the timeheadway of saturation flow is mainly affected by the position of pedestrians and the degree of pedestrians’ influence is classified into four levels. Then the speed-time profile for the vehicular acceleration at each level is fitted by Curve Fitting Software. Based on the effect to the time-headway and acceleration time, the model of capacity influenced by pedestrians is established and the influence is quantified, which enriches the fundamental theory of traffic engineering. The result shows that the vehicular capacity can be decreased by 14% at the worst case (level I). The conclusions obtained in this paper are valuable for better management of the signal intersect ion.