A packet forwarding method, a packet forwarding device, and a packet forwarding system are provided. The method includes: acquiring, by a first board, a source media access control (MAC) address and an input port number in a packet, and looking up a MAC address table according to the source MAC address; learning the source MAC address if no same entry is found; and looking up a forwarding policy table according to the input port number to acquire a forwarding policy, and sending the packet to a second board according to the forwarding policy, so that the second board learns the source MAC address to realize synchronization of MAC addresses. The synchronization of MAC addresses is realized by acquiring the forwarding policy without changing a current forwarding process or influencing an execution efficiency of a central processing unit (CPU).