The invention discloses a water leakage detection device for a diaphragm gas meter movement and a leakage detection method and belongs to the technical field of leakage detection of diaphragm gas meter movements. The water leakage detection device for the diaphragm gas meter movement comprises a positioning bracket and a control gas path, wherein the positioning bracket is used for positioning andsealing the diaphragm gas meter movement; the control gas path is connected onto the positioning bracket; a gas pipe joint communicated with each cavity of the movement is arranged on the positioningbracket; the gas pipe joint is connected with the control gas path. The leakage detection method comprises the following steps: positioning and sealing the diaphragm gas meter movement, putting a leakage detection device provided with the movement into clean water, introducing high-pressure gases into the movement, and observing the phenomenon in the clean water for judgment. The water leakage detection device for the diaphragm gas meter movement and the leakage detection method disclosed by the invention have the beneficial effects that the leakage detection device is simple in overall structure, the movement is convenient to position and place, the water leakage detection operation completed by the device is convenient, and the position of a leakage point in the cavity of the movement can be intuitively displayed. Moreover, each cavity in the movement can be detected, and the detection efficiency is improved.