Agonistic behavior and hierarchical formation of the Przewalski's Horse(Equus przewalskii) was conducted from the last ten-day in May to the last ten-day in June,2007,when a new herd was formed and released into the second reintroduction site in Kalamaili Ungulate Reserve,Xinjiang.Focal sampling and all-occurrence sampling methods were used to observe and record the agonistic behaviors of the herd,and the dominance index of each individual was calculated.No significant correlation was detected between the age and the aggressive behaviors frequency(r=0.60,t=1.62,r<r_0.05),however,a significant correlation between the age and the surrender behaviors(r=0.88,t=6.75,r>r_0.05) was found.There was no significant correlation between the aggressive and the surrender behaviors(r=0.56,t=1.41,r<r_0.05) among individuals in the herd.The master stallion had the highest dominance index,while females in the group had a linear series ranks corresponding to its age(r=0.94,t=13.99,r>r_0.05).The frequency of agonistic behaviors between individuals decrease gradually from coalition to releasing period,and the hierarchy formed and stabilized gradually.