The invention belongs to the field of semi-continuous spinning, and in particular discloses a pimple-free silk falling method applied to a semi-continuous spinning machine, which comprises the following steps of: A, breaking silk; B, sucking the silk into a silk suction device by adopting the silk suction device; C, taking a spinning cake out; and D, reversing the head. In the invention, the conventional silk falling method for the semi-continuous spinning machine is changed, and security problem caused by the use of iron cutters in silk falling is solved. Through pimple-free silk falling technology of the invention, a process of scraping silk waste pimples by using the iron cutters in the silk falling is saved, silk falling time is shortened, silk waste produced in the silk falling is reduced, the quality problem, caused by the silk waste produced by scraping the silk waste pimples in the silk falling, of rough pimpled silk is simultaneously solved, and the silk waste is directly sucked into a silk waste bucket.