The invention discloses an arc-shaped sloping roof contour plate construction structure and a construction method thereof, and belongs to the technical field of building construction. The arc-shaped sloping roof contour plate construction structure comprises an H-shaped steel beam, a contour plate assembly, a short L-shaped folded plate and a long L-shaped folded plate, the contour plate assemblyis arranged on the upper portion of the H-shaped steel beam, and the H-shaped steel beam and the contour plate assembly are connected through the short L-shaped folded plate and the long L-shaped folded plate; and the contour plate assembly comprises an obliquely-arranged contour steel plate, a plurality of sets of longitudinal truss ribs, a plurality of longitudinal bottom ribs and a bidirectional reinforcing mesh arranged on the upper portions of the longitudinal truss ribs. According to the arc-shaped sloping roof contour plate construction structure, the contour steel plate is tightly andfirmly fixed to the H-shaped steel beam in a slope environment, so that the construction safety is ensured; after a roof cast-in-place slab is poured, the contour steel plate and a concrete structureare stressed to work together, and the consumption of concrete between the steel beam can be reduced; and finally, the purposes of using the concrete as a cast-in-place slab bottom mold in the slope environment, shortening the construction period, reducing the construction cost and increasing the benefits are achieved.