The invention discloses a gas fixed-value checking table for simulating heavy gas fault realization of a transformer and a gas fixed-value checking method. The gas fixed-value checking table comprises a pressure excitation source, an insulating oil buffer, a flow velocity measuring device and a control center, wherein the pressure excitation source is used for allowing oil flow of generated insulating oil to pass through a connecting pipeline for pushing a gas relay to actuate and trip; the insulating oil buffer is used for storing the insulating oil which passes through the gas relay; the flow velocity measuring device is arranged on the connecting pipeline and used for measuring instantaneous flow velocity of the oil flow of the insulating oil; the control center is used for receiving instantaneous flow velocity data of the flow velocity measuring device, recording the instantaneous flow velocity, receiving an actuating and tripping signal of the gas relay at the same time and further controlling the opening and closing of an electric valve. According to the gas fixed-value checking table, a fault drive source of the gas relay is simulated by injecting compressed air to reach a certain pressure and then suddenly releasing the compressed air, a real state of gas action is directly stimulated, the precision of the measured instantaneous flow velocity is relatively high, and the purpose of quantitatively detecting the flow velocity value of a heavy gas protection action and the gas volume value of a light gas protection action is achieved.