The invention relates to a processing device for performing single-yarn pre-twisting in Siro-spinning and a processing method for performing single-yarn pre-twisting in Siro-spinning and based on the processing device. The processing device and method has the advantages that two groups of friction rotation roller devices vertical to a sliver transfer direction are added between a twisting convergent point and a front roller front jaw so as to solve problems in the Siro-spinning; the device adds false twist to single-yarn slivers through rotation, two single yarn is allowed to have sufficient pre-twist before twisting and plying by utilizing twist transfer, and twisting is performed on surface hairiness; vertical fluctuation degree of yarn sections, not controlled by external force, between the convergent point and a twisting device is reduced evidently under the support effect of the two groups of friction rotation rollers, and the yarn evenness of the Siro-spinning is increased favorably.