The utility model provides an external pressure bellows expansion joint with leak testing and safeguard function, the outside with the regional export end links of being connected of non -pressurized is fixed with the sealing ring, be equipped with the clearance between sealing ring and the outlet pipe, the sealing ring, export end links lateral surface, the outer periphery of outlet pipe encloses the emergent packing seal chamber that circularizes, be equipped with a plurality of sealing filler filling nozzle that annotate the material to emergent packing seal chamber on the sealing ring, the one end and the emergent packing seal chamber intercommunication of drainage tube, its other end corresponds water alarm device and sets up. The utility model discloses be applied to heat supply pipe network's long straight tube way, in time report to the police when the operation in -process takes place to leak to in time take emergent area and press safeguard procedures, make the pipeline continue the safe operation and change again until stopping warm period or turn(a)round.