Aiming at the fault of electronic communication equipment, which is difficult to reproduce and lacks test data and prior knowledge, a fault diagnosis method based on simulation model is proposed. First, the simulation model of the fault system is established, and the model is simplified as far as possible. Then the model is used to simulate the hypothetical fault causes one by one, and to observe the output of each key node at the same time. Finally, find the most consistent or similar results with the existing test data, and improve the simulation model. On this basis, the failure mechanism is analyzed, and the fault diagnosis is completed. This method can be used as a supplementary means of fault tree analysis which is a forward logic reasoning method and is opposite to the fault tree analysis method, and plays an important role in the fault diagnosis of a voice radio.