Abstract: In parallel and distributed systems, non blocking communications among multiple nodes are very important. The Clos Type network can satisfy this need quite well, so it is being used widely. But most of the multiple multicasts in this network are now accomplished by implementing the one to many communications step by step according to the input ports. The efficiency of this technique is low, and, in an N×N Clos Type network, the time complexity of the multicast routing algorithm using this technique is Θ（N 3/2 ） , and here N is referred to as the total number of input ports. In this paper, the sufficient condition of non blocking multiple multicasts in the Clos Type network is studied. And by using the grouping, competing and mutex schemes, the time complexity of the multicast routing algorithm in this network is reduced to ΘN log N loglog N 2log N , while the number of the switches in the middle stage of the network remains the same as above. Thus non blocking multiple multicasts in the Clos Type network are accomplished with quite lower time complexity.