Hydraulically powered gas injection valve

The invention discloses a hydraulically powered gas injection valve which comprises a valve body and a valve element, wherein a valve bush is arranged in the valve body; an electromagnetic valve communicating with an inner cavity of the valve body is mounted at the external part of the valve body; a valve rod of the valve element and the valve bush are in sliding fit; the valve rod is provided with a first stretching part and a second stretching part stretching out of the valve bush; the first stretching part of the valve rod is fixedly connected with a magnet through a magnet seat; a magnetic field sensor is fixed in the valve body and corresponds to the magnet in position; and a sliding guiding device is arranged between the valve rod and the valve bush. The magnet is fixed with the valve element through the magnet seat and moves along with the valve element, and the magnetic field sensor detects variation of a magnetic field to sense the stroke of the valve element so as to accurately control opening of th