Abstract: Based on the simple network management protocol (SNMP) MIB-II standard, this article proposed a network topology discovery algorithm. The algorithm can quickly discover the topology of the target network by combining the results of network layer and link layer topology discovery, connect the information accurately to the port, solve the problems of subnet information redundancy and the address forwarding table information incomplete in the topology discovery process. The experimental results showed that the algorithm could discover the network topology accurately, and had a good performance in connection accuracy, topology discovery efficiency and accuracy.