A segmented direct gate drive circuit of a depletion mode GaN power device, a gate voltage of the GaN power device is charged from a negative voltage turn-off level to a threshold voltage of the GaN power device; when the gate voltage of the GaN power device is charged to the threshold voltage of the GaN power device, a current mirror charging module first turns on less than N of charging current mirror modules to charge the gate voltage of the GaN power device from the threshold voltage of the GaN power device to a Miller platform voltage of the GaN power device, and turns on N charging current mirror modules to charge the gate voltage of the GaN power device from the Miller platform voltage of the GaN power device to a zero level.