The device is a mobile double-arm medium-speed sand mixer, used to mix furan type resin self-hardening sand. The machine is easy to operate, suitable for large-area, medium and large casting sand mixing molding. The corresponding auxiliary machine can form a medium and large molding mechanized assembly line. The machine is composed of trolley, machine base, boom screw conveying, sand mixing tank, liquid material system and air control system, and the sand mixing tank and boom can be rotated by maneuver to ensure sufficient modeling coverage area.