An embodiment of the present invention relates to the technical field of networks, in particular to a testing method, device and system for testing the performance of a Deep Packet Inspection (DPI) device. In this method, a performance analyzing device respectively acquires packet transmission characteristics of packets when being directly forwarded and packet transmission characteristics of the packets having been processed by the DPI device; and a test result on the performance of the DPI device with larger reference significance is acquired by comparing the two packet transmission characteristics.