An auxiliary support device for a rolling-cut shear, including: a lower cutting table; a plurality of first hydraulic support cylinders, a plurality of support plates, a plurality of second hydraulic support cylinders shorter than the first hydraulic support cylinders, a slide plate, and a plurality of horizontal hydraulic cylinders. The lower cutting table includes a first front end including a first mounting groove, and a second mounting groove, and an inner plate. The bottom wall of the second mounting groove includes a plurality of first bolt holes and a plurality of first recesses. The inner plate is embedded in the second mounting groove through a plurality of bolts passing through the plurality of first bolt holes. The inner plate includes a plurality of second bolt holes and a plurality of second recesses. The plurality of support plates lean against the inner plate.