The invention discloses an aluminum water mixing and degassing device for mechanical casting. The device comprises a casting furnace and a fixing seat, wherein the fixing seat is fixedly arranged on one side of the outer wall of the upper end of the casting furnace, a graphite connecting rod is inserted in the casting furnace, the outer wall of the end, extending outwards, of the graphite connecting rod is sheathed with a supporting plate, the outer wall of the lower end of the graphite connecting rod is connected with an annular clamping block in a threading manner, a plurality of groups of screw shafts are uniformly arranged at the outer wall of the annular clamping block in a surrounding manner, a breather pipe is arranged in the inner wall of the graphite connecting rod in a penetrating manner, a plurality of shunting pipes are communicated with the end, extending into a bottom support, of the breather pipe, an air inlet pipe is inserted into the inner wall of one end, far away from the shunting pipes, of the breather pipe, one end of the supporting plate is fixedly connected with a movable block, a screw rod is inserted in the middle of the movable block, and the screw rod is in threaded connection with the movable block. The device has the advantages of being simple in structure, easy to operate, and capable of fully mixing aluminum water in the casting furnace so as to purify the aluminum water and improve the quality of castings.