1. A method of storing a policy in a pattern matching apparatus comprising: configuring at least one processor to perform the functions of: (a) storing an original traffic pattern in the pattern matching apparatus and generating a content structure for a specific string pattern as a substructure of a header combination structure of a subsequently stored traffic pattern which is a policy to be newly applied to the pattern matching apparatus, wherein the header combination structure with a header index is a combination structure of traffic pattern segments related to header information; (b) determining whether a content of the subsequently stored traffic pattern is identical to a content of the original traffic pattern stored in advance in the pattern matching apparatus; (c) allocating a content index of the content of the original traffic pattern to the content of the subsequently stored traffic pattern if the content of the subsequently stored traffic pattern is identical to the content of the original traffic pattern; and (d) determining whether a header combination structure of the original traffic pattern comprises only one content structure or more than one content structure and allocating a header index of the header combination structure of the subsequently stored traffic pattern to the header combination structure of the original traffic pattern by replacing and merging a different header index of header combination structure of the subsequently stored traffic pattern corresponding to said newly applied policy with a same header index of header combination structure of the original traffic pattern in response to the header combination structure of the original traffic pattern containing only one content structure.