The invention relates to the technical field of metal casting molding, and discloses a cylinder cover casting mold opening mechanism. A fixed mold and a movable mold are attached to be internally provided with a mold cavity, a jetting hole communicated with the mold cavity is formed in the fixed mold, the movable mold comprises a first movable mold body and a second movable mold body, and a core rod connected to the second movable mold body is arranged in the mold cavity; a limiting hook is hinged to the first movable mold body, a circular bead corresponding to the hooking end of the limiting hook is arranged on the second movable mold body, and a limiting rod is arranged on the fixed mold and penetrates a through hole formed in the limiting hook; a gap is reserved between the limiting rod and the through hole, a shaft shoulder is arranged at the limiting end of the limiting rod, the limiting rod is sleeved with an elastic piece, and the elastic piece is clamped between the limiting hook and the fixed mold; and a screw is connected to the second movable mold body in a threaded manner, the other end of the driving end of the screw is rotationally connected to the fixed mold, and a hand wheel is connected to the driving end of the screw. By means of the scheme, secondary demolding is more stable and reliable; and meanwhile, the structure is quite simple, and manufacturing, installation and maintaining are convenient.