The invention discloses a DPI (deep packet inspection) method based on a regular expression. The DPI method based on the regular expression achieves regular expression matching of a high speed network through hardware, improves speed and flexibility for packet inspection, and is suitable for the packet inspection of the high speed network above 10G. The DPI method based on the regular expression uses a system which comprises a protocol inspection module, a flow list item maintenance module, a format encapsulation module, a data transmitting module, a regular expression matching module, a data receiving module, a format de-encapsulation module, a traffic shaping module, an interface configuration module, a result output module and an external memory module. The DPI method based on the regular expression is a method for achieving the regular expression matching on an FPGA (field programmable gate array), and the regular expression matching based on the FPGA not only can meet the request for high speed traffic, but also can continuously keep up with new development, and is low in realized cost. According to the DPI method based on the regular expression, the FPGA is used to achieve regular expression matching engine design, intrusion data is detected through a parallel pipeline mode, detection efficiency of data is improved, and overall improvement of detection performance of the system is achieved.