An embodiment of the invention discloses a determination method for an inversion circuit input voltage. The inversion circuit provides output for a gradient coil in a magnetic resonance system; a circuit topology in the inversion circuit is formed by a power switching tube; the control method comprises the steps of obtaining an inductive voltage value at the highest current value in a current sequence according to a relation between the inductive voltage and the inductive current in the gradient coil; and determining the minimum direct current voltage value of the inversion circuit input voltage when the output voltage is the inductive voltage value according to the relation between the output voltage and the input voltage of the inversion circuit, wherein the minimum direct current voltage value is a target input voltage when the inversion circuit processes the current sequence. By lowering the direct current input voltage, the loss of the power switching device in the inversion circuit can be reduced, and the junction temperature fluctuation of the device can be lowered, thereby prolonging the service life and improving the reliability of a whole gradient power amplifier.