A shut-off nozzle for hot runner systems of injection molding machines and a method of controlling the same are disclosed. The shut-off nozzle includes a nozzle body (1) having a resin hole (2), a heater (4), and a thermocouple (3) to sense a temperature of the nozzle body (1); a gate tip (8) having a nozzle gate (7) at which the nozzle body (1) comes into contact with a cavity (10) of a mold; a heating unit (5) provided around the gate tip (8) to heat the gate tip (8) by using electricity; and a cooling unit (6) provided around the gate tip (8) in parallel to the heating unit (5), so that a coolant passes through the cooling unit (6) to cool the gate tip (8). In the control method, the nozzle body (1) is primarily heated to a predetermined high temperature by turning on the heater (4). In addition, the gate tip (8) is heated by turning on the heating unit (5), prior to injecting a molten resin into a cavity (10) of a mold through the nozzle gate (7). The heating unit (5) is, thereafter, turned off after an injection of a predetermined amount of the molten resin into the cavity (10) of the mold is completed, thus allowing the gate tip (8) to start to cool. In addition, the cooling unit (6) is operated to quickly cool the gate tip (8). The mold is opened to remove a molded product from the cavity (10) of the mold.