Human relationships are a common characteristic of pedestrians and have important effects on evacuation behavior. Moreover, the presence of leaders also affects the evacuation efficiency of the crowd. Few scholars considered the influence of social relationships and leaders on group evacuation behavior. Motivated by the need an optimization model named PD-SLEM is proposed for simulating the outdoor crowd evacuation during earthquake considering the impact of social relationships and leaders. Depending on the willingness to escape together with partners, multiple social relationships are abstractly classified into three aggregation relationships. Experiment results demonstrate that leaders in the crowd, especially professional disaster relief volunteers, significantly improve the evacuation efficiency.