Abstract: This paper presents the network architecture of KM7A, which is the largest horizontal space environment simulator in China. The stacking network and the LACP (link aggregation control protocol) are applied in this network. All pivotal equipment are channel bonded via the LACP to realize the redundancy of the key equipment and the data channel, to reduce the switching time of the data channel for the active-standby test network, to avoid the single-link failure, and to advance the stability and fault tolerance of the data transmission link.