Provided is a cut-tobacco impregnation and expansion system, comprising a delivery device (200); the upper part of the delivery device is provided with an impregnation tank (100), and the lower end of the delivery device is connected to a tobacco expansion device (300); the lower part of the impregnation tank is connected to a medium storage tank (62) by means of a medium recovery pipe (6); the top part of the impregnation tank is connected to the medium storage tank by means of a medium spray pipe (8); the delivery device and/or tobacco expansion device is connected to a negative-pressure device by means of an exhaust pipe (4); the outlet of the negative-pressure device is connected to a medium storage tank (10) by means of a secondary medium recovery pipe. A negative-pressure device is used to compress and recover the gaseous medium evaporated from the impregnated tobacco when same is in the delivery device and/or expansion device, reducing the waste of the vaporized medium.