Abstract: There is disclosed an improved sliding exhaust brake system installed on a large vehicle. The brake system comprises a housing, an exhaust gas passage, a main valve member taking the form of a flat plate, one or more exhaust pressure-adjusting holes formed in the main valve member, an auxiliary valve member, and a holding mechanism. The main valve member engages the piston rod of an air cylinder device. The auxiliary valve member can move a given distance relative to the main valve member. When the exhaust gas passage is opened or closed by the main valve member, the auxiliary valve member opens or closes the adjusting holes. At this time, the holding mechanism temporarily prevents relative movement between the the two valve members.