The invention relates to a casting mould locking mechanism comprising a casting mould and a locking assembly, wherein the locking assembly is fixed on the wall of a pit; the locking assembly comprises a base fixed on the wall of the pit, a connecting rod connected onto the base, a cross beam and positioning pins, wherein a plurality of pin holes are arranged on the connecting rod; both ends of the cross beam are respectively provided with installation grooves; the cross beam is sleeved onto the connecting rod through a positioning groove; and the positioning pins penetrate through the pin holes to position the cross beam and are perpendicular to the installation grooves. The invention solves the technical problems of difficult operation and poor counterweight effect in the traditional method for pressing a casting mould cover box depending on a heavy foundry weight; in addition, according to the invention, simple structure is realized, and manpower and material resources are saved by locking the casting mould cover box by moving the cross beam.