The dry-type air-core series reactor is an important component in the reactive power compensation loop of a power system. Its main insulation usually adopts an epoxy casting structure. It is difficult to set the inter-turn insulation fault and the test verification cost is high. There is a need to monitor whether turn-to-turn short-circuit faults occur and improve online monitoring sensitivity. In this paper, the finite element software Comsol is used to simulate the changes of electrical parameters when inter-turn short circuits occur. First, the inductance and current values of the reactor under normal conditions are simulated and calculated, and the correctness of the model is verified by comparing with the results obtained by analytical calculation methods. Then the inter-turn short-circuit fault points at different positions are set to obtain the current of each coil layer of the reactor. Finally, the change of electrical parameters such as equivalent resistance, reactance, mpedance, and power and loss factors of the reactor is calculated. The simulation analysis shows that the different electrical parameters of the reactor have different rates of change because of different short-circuit locations. The absolute values of the reactor have a tendency to increase from the end to the middle and from the inner layer to the outer layer. Among the parameters, the change rate of the loss factor of the reactor and power factor change rate are large, and sensitive to reactor short-circuit faults between turns. The system can be used for on-line monitoring and protection of inter-turn short-circuit faults in dry-type air-core series reactors. This work is supported by the National “Thirteen-Five Year” Research and Development Program of China (No. 2016YFB0901303).