A bypass adjusting device for a gas outlet end of a high-temperature gas heat exchanger comprises a baffle, a heat exchange tube valve plate, a bypass tube valve plate, a transmission rod and a transmission mechanism. The sides, close to the tube plate, of the baffles are connected with the barrel to form a heat exchange tube outlet cavity and connected with the bypass tube to form a bypass outletcavity, and the two cavities are independent of each other. The side, away from the tube plate, of the baffle and the barrel form a mixed gas outlet cavity; the heat exchange tube valve plate is matched with the baffle to form a heat exchange tube channel outlet, and the bypass tube valve plate is matched with the baffle to form a bypass tube channel outlet; and the heat exchange tube valve plateand the bypass tube valve plate are linked by a transmission rod and a transmission mechanism. By operating the transmission rod and adjusting the opening degree of the valve plate, the local resistance coefficient and the circulation area of medium flowing of the heat exchange pipe and the bypass pipe are changed, the adjusting amplitude and the adjusting precision of the gas temperature are improved, and the gas temperature adjusting device is suitable for occasions with control requirements for the gas outlet temperature.