This paper introduces an idea that solves the synchronization problem in the process of application-level multicast routing without using the dedicated synchronizing controller. Furthermore, the low-delay multicast communication is achieved on base of an idea. The contributions of this paper include: (1) The process of multipoint synchronizing interaction is modeled, and the theorem of application-level multicast routing algorithms supporting multipoint interaction synchronization is proved; (2) An effective low-delay multicast routing algorithm that supports multipoint interaction synchronization is proposed; (3) Performance analysis of this algorithm and the existing similar algorithm is carried out by mathematic methods. Both simulation experiments and practical applications demonstrate that the algorithm is correct and effective.