Packet classification is an important building block of the Internet routers for many network applications. In this paper, we propose a scheme called Layer Partitioned Search Tree (LPST) to solve multi-field packet classification problem. LPST improves the traditional decision tree based schemes (e.g. Hyper Cuts and EffiCuts) by reconstructing the leaf nodes of the decision tree as an approximately balanced search tree. The rules may be stored not only in the buckets of leaf nodes but also in the internal nodes of LPST. Thus, searches on LPST may be completed immediately without searching all the buckets on the path to some leaf node if the packet already matches an internal node. The experimental results show that LPST requires less memory storage even if LPST categorizes the rules by two fields to reduce rule duplication rather than five fields in EffiCuts. Besides, in terms of number of memory accesses, LPST is better than Hyper Cuts and EffiCuts.