The invention discloses a fixture applicable to mounting of a replaceable waterproof rubber belt. The fixture comprises a framework plate, and a pulling rope is mounted at one end of the framework plate; a first hinge pin and a second hinge pin are penetratingly fixed to the surface of the framework plate, front extrusion rollers are fixedly mounted at two ends of the first hinge pin, and rear extrusion rollers are fixedly mounted at two ends of the second hinge pin; a distance between the front end of the framework plate and the circle center of each front extrusion roller and a distance between the front end of the framework plate and the circle center of each rear extrusion roller are smaller than radiuses of the front extrusion rollers and the rear extrusion rollers respectively; a distance between the rear end of the framework plate and the circle center of each front extrusion roller and a distance between the rear end of the framework plate and the circle center of each rear extrusion roller are larger than radiuses of the front extrusion rollers and the rear extrusion rollers respectively. By interaction of the front and rear extrusion rollers, a waterproof rubber belt connection lug can be extruded into a small cavity, and accordingly mounting efficiency is improved. In addition, by the aid of guide wheels, slide resistance of the fixture is reduced, and mounting efficiency and quality of the waterproof rubber belt of a retractable device are improved.