An effective measurement method for gate charge characteristics of MOSFET under high power was proposed. During the turn-on process of the lower transistor in a half-bridge circuit, a large drain current and a high drain-voltage would occur, producing a much high transient power. For the traditional test technique, not only an equal high power is required for the DC source used, but also a serious self-heating effect cannot be eliminated. Both of them lead to inaccurate gate charge curves. In this paper, based on the basic physical process and relationship of gate charge test, the gate charge characteristics of MOSFET under high power were obtained by measuring the characteristics of gate charge under high voltage-small current and high current-small voltage. The results showed that the characteristic curve and the parameters obtained by this proposed method were nearly close to the values given by the standard specification, which had good industrial application value.