This study surveys the fiber behavior in yam formation and the physical properties of Solo-spun yam. The specimens were made by six types of Solo-spun rollers with fixed twist multiplier. The physical properties such as yam count, evenness, strength, and breaking elongation of these yams were compared with the properties of ring spun yams and analysed with the mechanism of Solo-spun yarn formation. The grooves on the surface of Solo-spun roller divide the web and interfere the twist propagation. These phenomena cause the uneven draft and the fly of fiber, so the Solo-spun yam becomes finer than fing-spun yam and the yam breaking strength and elongation deteriorate, but these demerits can be improved with rounding the protruded edge of Solo-spun roller grooves.