Abstract: For the blockchain fork in blockchain networks can cause the attacker to perform double-spending attack very easily, how to reduce the fork probability is a very important and challenging research issue. Aiming at three problems of current research on optimizing the propagation mechanism of transactions and blocks in blockchain networks to reduce the fork probability: only the propagation delay between adjacent nodes or the total number of routing hops of the propagation process is reduced; the propagation process generates a large number of communication messages; it is based on the assumption that nodes on the propagation path will continue to propagate transactions and blocks, and a propagation mechanism combining an optimal propagation path and incentive (OPPI) in blockchain networks, is proposed to decrease both the total propagation delay and the number of communication messages, which achieves a tradeoff between the propagation efficiency and the propagation cost. Simulation results show that: compared with the existing propagation mechanism of blockchain networks based on Gossip, when the network topology is random graph, scale-free graph, small-world network graph, the number of nodes is 10, 100, 1 000, 10 000 and the degree k is set to 2, 4, 8 respectively, OPPI reduces both the total propagation delay and the number of communication messages generated by the propagation process significantly, specifically, by 99.4% to 99.98% in the total propagation delay and by 99% to 99.1% in the number of communication messages.