Dam overflow weir crest cover mold and construction method

The invention provides a dam overflow weir crest cover mold and a construction method. The dam overflow weir crest cover mold comprises a steel pipe and a steel form which are arranged in a layered mode from top to bottom; the steel form is of a curved structure and formed by assembling a plurality of unit molds; a plurality of pairs of first outer keel structures perpendicular to the steel pipe are arranged on the upper side of the steel pipe and arranged at equal intervals; each pair of first outer keel structures are connected together oppositely in a spot welding mode; each pair of first outer keel structures are welded with the steel pipe; a plurality of second outer keel structures vertically intersecting with the first outer keel structures are arranged on the upper layers of the first outer keel structures; and the second outer keel structures are arranged at equal intervals and welded to the first outer keel structures. The construction method comprises the steps of S1, pretreatment, S2, rebar erecti