Siro spinning is to feed two rovings on the spinning frame, and two roving slivers with a certain distance in parallel are drawn by rollers in the spinning drafting area, and then two small triangular areas are formed at the front roller nip, and then they are gathered together and twisted into a yarn strip. Due to the transmission of twist, two strands have been twisted back on a single strand before twisting, so the twisted yarn has a different strand style from the general single yarn. If the yarn-dyed roving is used with feeding, the patterned "AB" blended yarn can be spun.