The utility model discloses a device for recycling low-grade heat energy. The device comprises rectifying towers which are sequentially arranged, Gas-phase condenser, Intermediate medium evaporator, Screw expansion generator set, wherein the gas-phase condenser comprises a first medium inlet; First medium outlet, a second medium inlet and a second medium outlet, the intermediate medium evaporatorcomprises a third medium inlet; Third medium outlet, The upper portion of the rectifying tower is connected with the first medium inlet through a line pipeline, the second medium outlet is connected with the third medium inlet through a line pipeline, the third medium outlet is connected with the second medium inlet through a line pipeline, and the fourth medium outlet is connected with the screwexpansion generator set through a line pipeline. The device can effectively utilize the middle-low-grade waste heat of the high-temperature gas phase at the top of the rectifying tower to achieve thepurposes of energy conservation and consumption reduction.