At present, the network has gradually become the foundation of information construction. People have more demands for network topology management. The increasing scale of network topology and the heterogeneity between devices and protocols have brought great difficulties to network topology discovery. This paper proposes a knowledge-based reasoning Network topology discovery method. This method uses multiple heterogeneous data sources, uses computer network prior knowledge to construct a knowledge base from top to bottom, uses inference learning to establish reasoning rules, and then constructs a multi-level network topology structure.