A packet diversion method and a DPI device are disclosed in the present invention. The method includes: receiving a packet, where the packet contains a user identifier; according to the user identifier and preset first correspondence between the user identifier and a service type, searching for the service type corresponding to the user identifier in the packet; adding an inner virtual local area network Vlan header to the packet according to the service type, preset second correspondence between a service type and a slave device identifier, and preset third correspondence between a slave device identifier and each bit in a diversion identifier field; and diverting the packet to a corresponding slave device according to the diversion identifier in the diversion identifier field. The inner Vlan header carrying the diversion identifier field is added to the packet, to indicate diversion of the packet in a same cluster.