The present application provides a packet processing method, device and system. A controller sends a first flow entry to a network device. The first flow entry comprises first importance information used for indicating importance of a first flow entry, where the first importance information is used by the network device to determine, according to a second importance information of a second flow entry in the flow table and the first importance information of the first flow entry, whether to add the first flow entry into a flow table of the network device when there is no idle flow entry resource in the flow table.