For the study of spectroscopy, lasers which have high power and resolution are needed. Spatial hole burning of population differences by standing wave is ruled out by using ring type cavity. Three stage birefringent filter tuned smoothly in the operational range of dye molecule. When pumping power is 3.2W, Single mode output is 210mW which is 40% of multi-mode output power. A semiclassical discription for Ring dye lasers is described where the energy level diagram of the dye molecule is assumed to be 2-level system. Unidirectional and bidirectional single mode operation is discussed. The linear-stability analysis for these operations reveals that unidirectional operation is stable for all case. But bidrectional operation is stable under some districted conditions.