This paper studies the working principle of Linux Virtual Server (LVS), and analyzes its data forward process. To make LVS deployable in the environment of multiple VLANs (Virtual Local Area Network), this paper designs and implements a data forward method naming Double-NAT based on Network Address Translation(NAT). The Double-NAT method organizes the connection hash table in double-direction hash bucket, and uses system allocated port to distinguish data flow of IN and OUT direction, thus data in multiple VLANs can be forwarded via network address translation. Test results show that Double-NAT data forward method makes LVS work well in multiple VLANs environment with easy configuration and good performance.