The invention discloses a bonding method for a jet pipe and a flexible plug cover of a solid rocket engine, and a sealing tool. The bonding method includes the steps that after the flexible plug cover and a jet pipe throat lining are bonded in advance, the sealing tool is mounted on the jet pipe, and the flexible plug cover and the sealing tool are matched to form a first sealed space area; and the first sealed space area is pressurized, the external molded surface of the bonding surface between the flexible plug cover and the jet pipe throat lining is pressurized in an air-pressure mode, and finally, pressure-maintaining solidification is carried out. By utilizing the non-directionality of air pressure, air pressure is applied to the flexible plug cover and acts on the external molded surface of the bonding surface, all points on the bonding surface are subjected to normal-direction stressing, surface-contact uniform stressing of the bonding surface is achieved, and therefore the bonding quality is improved; and in addition, the method is simple, operation is convenient, the period is short, the cost is low, and the bonding method is especially suitable for bonding of the jet pipe and the flexible plug cover of the large-diameter solid rocket engine.