Abstract: A yarn twisting method and device for a ring spinning machine is provided. The twisting method comprises the following steps: feeding three roving strands (1, 2, 3) into a back roller (8) of the ring spinning machine; after drafting, the three roving strands, three fiber strands (1, 2, 3) exiting from a nip point of a front roller (10), wherein a fiber strand (2) in the middle forms an angle with a plane formed by the other two fiber strands (1, 3), and thus the three fiber strands (1, 2, 3) form a multi-strand spinning triangle region having a three-dimensional spatial form; and in the multi-strand spinning triangle region, the three fiber strands (1, 2, 3) obtaining twist by means of a ring traveler of the ring spinning machine, and the twisted fiber strands (1 ,2, 3) are combined into a composite yarn (4) through a convergence point.