The present invention relates to a dual venturi for a combustor and, specifically, to a dual venturi for a combustor, which adjusts the amount of gas and air supplied to a burner of a hot water heater and has a motor combined with a damper in order to increase a turn-down ratio (TDR), such that the damper is rotated by the driving of the motor so as to simultaneously open or close secondary air and gas inlets, thereby enabling efficient heating control. The present invention has a separate opening/closing means which is capable of controlling, in two stages, the amount of air and gas flowing into the combustor such as the hot water heater, wherein the opening/closing means comprises the motor and the damper, and the damper is rotated by the driving of the motor so as to simultaneously open or close the secondary air and gas inlets, thereby enabling the control of the amount of air and gas.