The Dual Population Ant Colony Algorithm is used to establish the multicast tree. One group searches from source to destination and the other from destination to source. The pheromone update rule is modified by the effect of QoS parameters and the optimal tree which meets QoS parameters is found. The effect of every QoS parameter is confirmed by orthogonal experiment of statistical. According to the scope of the search paths, a suitable orthogonal table of the orthogonal experiment is implemented. The experimental results show that the proposed algorithm can make full use of QoS resources and get the better result rapidly.