The embodiment of the invention discloses a short-circuit current calculation method and system, and the method comprises the following steps: S01, forming a basic database according to an actual power grid, and building a model of a set power grid operation mode; s02, scanning the short-circuit current level of the whole network; s03, solving each sequence impedance reduced to the short-circuit point by using a Newton method in combination with an iterative method, and solving the total current of the short-circuit point; s04, superposing the positive sequence component, the negative sequencecomponent and the zero sequence component of the total current of the short-circuit point to obtain a final short-circuit current; an inverter circuit, a control system and a boosting transformer control circuit are utilized. The positive sequence component, the negative sequence component and the zero sequence component can be superposed to obtain voltage and current of each phase; a set value of the internal potential of the inverter type photovoltaic power supply is generated through the step-up transformer control circuit recursive function, an overall mathematical model of a line power grid is established, the calculation amount is reduced, the calculation speed is increased, the calculation time is shortened, the operation efficiency is improved, the power supply safety can be improved, and the power grid can flexibly operate.