The invention discloses a membrane feeding device on a gas analysis mass spectrometer. The device comprises a membrane press box, a front end connecting flange and a rear end connecting flange, wherein a groove is formed on the front end connecting flange and the rear end connecting flange respectively; the membrane press box is closely matched through the grooves between the front end connecting flange and the rear end connecting flange; the contact faces of the membrane press box and front end connecting flange are respectively provided with a sample inlet for inflow of a sample molecule and a sample outlet for allowing the sample molecule to flow out; and the contact faces of the membrane press box and the rear end connecting flange are provided with mass spectrometric connecting pipes. According to the device, the replacement of the membrane press box is greatly facilitated; and furthermore, connection and disconnection between a buffer chamber and the mass spectrometric sample inlet can be realized by a vacuum isolating valve in the mass spectrometric connecting pipe, thus frequent destruction to the vacuum system of the mass spectrometer is avoided. The device can be widely applied to the field of gas mass spectrometers.