The invention provides a sinking delaying device used after wading sinking of an automobile. The device comprises a floating block, a detection control part, a gasholder, a solenoid valve and a bolt, wherein the floating block comprises a mounting seat, a gas generation device, a gas bag, a gas bag fixing rope and a sliding ball, the gas generation device is mounted at the top of the gas bag and communicates with the gas bag, an igniter is arranged in the gas generation device, a gas nozzle is mounted at the top of the gas bag and communicates with the solenoid valve and the gasholder through the gas nozzle, and the gas bag, the solenoid valve and the gasholder communicate in series. The device has the advantages of reliable structure and convenience in mounting and can quickly recognize the automobile wading sinking state, quickly spread the gas bag and reduce the sinking speed of the automobile; the gas bags are mounted in different position of the bottom of the automobile, and the gas bags mounted in different positions of the bottom of the automobile can be started sequentially, so that the automobile can be kept balanced in water, and the automobile is prevented from turning on one side in water.