The invention discloses an oil tank structure for an injection molding machine. The oil tank structure comprises an oil tank mounting position (2) located on the injection molding machine, an oil tank(3) and a support rod (4); a fixed guide rail (5) is arranged at the oil tank mounting position (2); the fixed guide rail (5) is axially connected with a movable guide rail (6); the movable guide rail (6) extends out of the oil tank mounting position; the two sides of the oil tank (3) are provided with rolling wheels (7) matched with the movable guide rail (6) and the fixed guide rail (5); one end of the support rod (4) is supported on the movable guide rail (6); and the other end of the support rod (4) is detachably fixed to the injection molding machine (1). Through sliding of the oil tankand the guide rails, sliding in and out from the side face of the oil tank mounting position can be achieved, and cleaning, maintenance and smoothness of the oil tank are facilitated.