The frequent occurrence of inter-turn short circuit faults of dry-type air-core series reactors in shunt capacitor sets gravely imperils the secure and steady operation of the power system. It is extremely crucial to research the variations of characteristic quantities prior to and subsequent to inter-turn short circuits in dry-type air-core series reactors. In this paper, Maxwell is used to establish the field-circuit coupling model, and the model accuracy is verified by comparing the calculated value of the analytical method with the test value of the manufacturer. On this basis, the inter-turn short-circuit model is constructed, and the electrical quantities when inter-turn insulation faults occur at different locations in different phases (inter-turn insulation aging phase and inter-turn short-circuit phase) are investigated. The results show that the absolute value of each electrical characteristic quantity increases with the change of fault location from the end to the middle in the inter-turn insulation aging phase and the inter-turn short-circuit phase. In particular, the loss factor and power factor have the largest rates of change, which can be used as electrical parameters for on-line monitoring of inter-turn short-circuit faults.