A novel tunable all-fiber laser using Er3+/Yb3+-doped single-mode fiber ring resonator has been demonstrated. In our specially designed all-fiber configuration, a tunable fiber coupler was used not only for coupling the Er3+/Yb3+-doped fiber to become a ring resonator but also for wavelength tuning. In addition, there are not any reflective elements in the laser so that the excess loss was very low. A wavelength tuning range of >70nm was obtained. The design and experimental results are reported in this paper.