The invention discloses a device and method for welding a fluoroplastic heat exchanger tube plate. A fluoroplastic tube bundle is arranged in a metal sleeve with a flange end. A connecting pipe is formed in the wall of the sleeve. One end of the sleeve is connected with an airtight sealing head, and the other end of the sleeve is connected with the inner wall of a constant temperature furnace. The bottom end of the tube bundle is inserted and connected in the tube plate, and an expansion limiting ring clamping assembly is installed on the periphery of the tube plate. After the constant temperature furnace is heated and the temperature is increased, vacuum pumping is conducted on the sleeve, the parts between the outer walls of fluoroplastic tubes and tube plate holes are in a low-vacuum state, and the outer walls of the melted fluoroplastic tubes and the inner walls of the tube plate holes of the fluoroplastic tubes can be sufficiently merged. By means of the device and method for welding the fluoroplastic heat exchanger tube plate, tube plate welding is completed, the welding strength between the tube bundle and the tube plate is high, the welding depth can reach 40 mm or higher, no defect exists on a welding face, the leakage rate is zero, the welding efficiency is high, and the welding reliability and the success rate of the fluoroplastic tube plate are greatly improved. By means of the method, low-vacuum negative-pressure pressurizing is adopted, the influences of the steel core machining precision on different welding holes when a tube bundle steel core is adopted for pressurizing are avoided, and the leakage rate is greatly reduced.