We report a high efficiency CW single frequency ring Ti:sapphire laser pumped by an argon ion laser. By 5.0 W pumping, more than 0.5 W stable single frequency output is attained. The conversion efficiency is over 10%. The characteristics of the intracavity frequency-control elements, the optical unidirectional device, the birefringent filter, and the etalons, are analyzed. The optimum pumping is discussed by considering the thermal effect produced by the Ti:sapphire. Also, the tuning range, the linewidth, and the output stability of the laser are measured.