The invention relates to a target spraying mechanical arm which comprises a Y-directional movable guide rail, a bearing platform, a Z-directional movable mechanism, two image acquisition cameras, an X-directional rotating mechanism and a spray beam, wherein the Y-directional movable guide rail is arranged in the Y direction parallel to the ground; the bearing platform is arranged on the Y-directional movable guide rail; one end of the Z-directional movable mechanism is connected with the lower part of a movable platform walking in an elevated guide rail and the other end is connected with theY-directional movable guide rail; the two image acquisition cameras are respectively arranged at both sides of the Z-directional movable mechanism; the X-directional rotating mechanism comprises a rotating support and a rotating shaft which rotates opposite to the rotating support; the rotating support is fixedly connected with the front side of the bearing platform; the axis of the rotating shaftis consistent with the X direction which is vertical to the Z direction and Y direction; the spraying beam is arranged on one end of the rotating shaft and is vertical to the rotating shaft; and a nozzle is arranged on a beam body. A Z-directional scissors lifting cradle and a Y-directional synchronous belt straight line guide rail form a two-dimensional movable platform on a vertical plane, thusrealizing the positioning of arbitrary positions on the vertical plane.