When selecting network security indicators, the conventional security situational awareness system ignores the impact of operation and maintenance index and assets on network security, resulting in a small number of attack events perceived by the system when network nodes are attacked. In order to solve this problem, this research designs a power monitoring network security situational awareness system based on knowledge map. In terms of system hardware, the overall system architecture is composed of data layer, function layer and interface layer, and the data collector is used to collect network security risk data; In terms of system software, the knowledge map graph is used to describe the network security risk data. After calculating the network security vulnerability index, assets, security event compensation and operation and maintenance index, the calculation results are used as the network security index to obtain the network security situation value. The test results show that the system can reflect the attack events in all attack stages, and the number of perceived attack events is significantly more than that of the conventional system, indicating that the system can effectively perceive the security situation of the power monitoring network.