With the rapid development of information and network technology, synthesizing several kinds of networks and supporting platforms become a trend to build virtual testing system. The key to construct this kind of large scale virtual testing system successfully lies in whether the supporting infrastructure can deliver data to participants in a timely manner. This paper devoted to the issue of unification and interconnection of virtual testing system. Based on the study of putting up various types of network environment and network layer interconnection program of large-scale virtual testing system, study the following: Hierarchical testing environment based on virtual shared memory mechanism. The middleware based on virtual shared memory mechanism is studied. Hierarchical testing environment applied virtual shared memory as main mechanism is presented. The large-scale virtual testing system which contains REVSM and VMICVSM is realized. These two kinds of middleware’s function and communication mechanism are discussed. Gateway mechanism which connects REVSM and VMICVSM is designed for putting up hierarchical testing environment.