Nowadays, many high speed Internet applications require high speed multidimensional packet classification algorithms. Based on the uniqueness of Network Processor, this paper presents a multidimensional classification algorithm—AM-Trie (asymmetrical multi-bit trie). AM-Trie is a high speed, parallel and scalable algorithm and very fit for the “multi-thread and multi-core” feature of the Network Processor. A heuristic field division algorithm is also presented, and it is proved theoretically that it can find out the minimum storage cost solution when the height of the AM-Tire is given. Finally, a prototype is implemented based on Intel IXP 2400 Network Processor. The performance testing result shows that AM-Trie is a high-speed and scalable algorithm; the throughput of the whole system is influenced little by the size of rules and it can reach 2.5 Gbps wire speed.