A life-saving device, including: a buoyancy bag including a cavity; a wearable member including a housing; a controller including a single-chip microcomputer, a battery, a flip-flop, and an integrated circuit board; a gas generator including an input electrode terminal and a gas outlet. The single-chip microcomputer includes a plurality of pins and is disposed on the integrated circuit board; the battery, the flip-flop, and the input electrode terminal of the gas generator are respectively connected to the plurality of pins through the integrated circuit board; the housing includes a first chamber, and the battery, the single-chip microcomputer, and the integrated circuit board are disposed in the first chamber; the cavity of the buoyancy bag communicates with the gas outlet; and the buoyancy bag is deflated when in nonuse for convenience of storage, and inflated with gas produced by the gas generator to expand in an emergency.