The invention provides a spinning device and method for untwisting roving and enhancing twisting of spun yarns. The spinning device comprises a drafting mechanism and a winding mechanism, wherein a yarn guide device is arranged between the drafting mechanism and the winding mechanism; a twisting device is arranged between the drafting mechanism and the yarn guide device; an upper sideband of the device is in contact with roving penetrating through a roving feeding bell mouth, to form a roving untwisting operation surface for untwisting the roving before drafting so as to reduce twisting redistribution phenomenon of the roving in the drafting process; a lower sideband is in contact with outputted fiber strands drafted by a front roller to form a pre-twisting degree and play a role of enhancing the pre-twisting of the fiber strands before twisting so as to reduce a twisting triangular region between a front roller jaw and fiber strand twisting points and improve the comprehensive quality of finished yarns.