Multi-cluster with NAT (network address translation) is a kind of building cluster of clusters (CoCs) in parallel processing, we can easily combine two or more PC clusters which had setting on difference place to form a big one parallel system to reach the acceptable performance and resolving the issue of insufficient public IP address. In this paper, it includes three parts: First we construct a CoCs with four PC clusters which connected with NAT on difference place in LAN environment. Second, we build a monitor system in our system in order to control and observe this system in a convenient way; this monitor system also has a client with mobile availability for users without computers. Third, we evaluate the system performance with different MPI parallel programs for the analysis of different parallel models