The invention discloses a route diffusion method for dynamically generating expansion tree in the network, specifically suitable for the scene of broadcast routing in an Ad hoc network or a Wireless Mesh Network. The invention adopts a method of combining broadcast table, neighbor table and sequence numbers on network nodes, to establish, update and delete the neighborhood relation among network nodes by timely transmitting call packets; and then transmits and forwards broadcast packets according to the setting criterion based on the real-time updated neighborhood. The packet transmission includes: after receiving the broadcast packet transmitting indication from the upper layer, the nodes stuffing packets, adding one to the present network node sequence number, and adding the node address, the node sequence number and neighbor node information in the packet heading, and then transmitting packets; and the packet forwarding includes: nodes receives the broadcast packet from network, looks for the generating nodes of the packets in the broadcast table, compares the sequence number in the packet and the size of the corresponding sequence number in the broadcast table to determine whether the packet is a redundant broadcast report, and then continues the packet forwarding. The route diffusion method for dynamically generating expansion tree in the network adopted by the invention can realize the effective spreading of the broadcast packet, and effectively inhibit the generation of broadcast storm and routing self-loop; the method has relative simple and practical protocol, application in micro scale networking, and fast network convergence rate.