The invention relates to technology for evaluating the state of electric transmission and transformation equipment, in particular to a system for evaluating the state of the electric transmission and transformation equipment based on a tree topological structure. The system solves the problem that at present, no system for evaluating the operating state of the electric transmission and transformation equipment in real time and making overhaul decisions according to the evaluation result is available. The system for evaluating the state of the electric transmission and transformation equipment based on the tree topological structure comprises a lightning locator, an overhead line temperature detector, an insulator dirt detector, a transformer oil detector, an electric energy quality detector, a transformer neutral point current detector, a data processing module, an online early warning module, an intelligent diagnosis module, a state evaluation module, a risk prediction module and an overhaul decision making module. The lightning locator, the overhead line temperature detector, the insulator dirt detector, the transformer oil detector, the electric energy quality detector and the transformer neutral point current detector jointly form branches of the tree topological structure. The system is suitable for power grids.