The invention discloses an alfalfa non-separation quick rooting and cutting device which comprises a cutting cup and a fixing device (3), the cutting cup comprises a cup body (1) and a cup cover (2), the cup body (1) is connected with the cup cover (2) in a threaded mode, and the center of the cup cover (2) and the bottom of the cup body (1) are each provided with a small hole with a diameter of one centimeter; the cutting cup is fixed on the fixing device (3), and the cutting cup is used for containing culture substrates. The alfalfa non-separation quick rooting and cutting device and an application method thereof further disclose an alfalfa non-separation quickly rooting cutting method, and the alfalfa non-separation quickly rooting cutting device and the application method thereof have the advantages of being high in efficiency and survival rate.