Abstract: High performance interconnect network has a significant influence on the performance of high performance computer. As the difference in network model design will result in different network performance, the early network simulation is needed. HPCSim is an independently developed high performance interconnect network simulator based on OMNeT++. It includes topology and parameter file generator named PySim, and simulation data analyzer and visualizer named PyVisual. An improved fully-buffered router structure is proposed, which achieves 5 stage pipeline, and reduces routing computation states buffer as well as promotes throughput from 0.75(baseline router) to 0.95. Moreover, a link model is inferred from photonic network, and the link performance simulation is run based on Fat-tree network to analyze the relation between link bandwidth and network throughput.