Abstract: A method for classifying a network packet includes the steps of: receiving a network packet which includes a plurality of specific data; providing a basic rule table which includes a plurality of basic rules corresponding to the plurality of specific data; providing a composite rule table which includes a plurality of composite rules corresponding the packet classes, and each of the composite rules includes a specific calculation; each of the basic rules generates an output result according to the corresponding specific data; each of specific calculation generates a calculated result of the corresponding composite rule according to part or all of the output results; determining the packet class of the network packet according to the calculated results.