The invention discloses a subpressure ignition control device which is hard to loss effect and is used for sintering an iron ore. The device includes an air box body, the vertical tube of the air box connected on the body of the air box as well as a large flue and a by-pass pipe connecting the vertical tube of the air box and the large flue; a clapboard is arranged in an access between the vertical tube of the air box and the by-pass pipe; the clapboard is fixed on the inner wall of the access so as to lead an air flow to pass through from the lower part of the access. A bending tube providedwith the clapboard is connected between the air box and the by-pass pipe to lead the air box to have the function of dust removing and lead a bulk to be deposited at the bottom part of the bending tube and to be incapable of entering the by-pass tube, thus avoiding the by-pass tube from plugging; an electric flap the opening of which can be controlled is arranged in the by-pass tube to control the subpressure of the lower surface of an ignition air box; the bottom part of the bending tube is provided with a double-layer ash discharge valve which is convenient for cleaning sediments. The subpressure ignition control device of the invention can flexibly and effectively control the subpressure of the ignition air box and the subpressure of a hearth, maintain the normal running of the sintering process, save the energy consumption for ignition and is applicable for the ignition and sintering of a sintering machine by a v-ti magnetite concentrate ore in particular.