A high-powered tunable Er-doped fiber ring laser, based on FBG (fiber Bragg grating), is reported in this article. It was pumped by 980 nm-laser diode. The line width of the output laser was less than 0.04 nm in 1562 nm band, and the tunable span was 4.6 nm. The reappearance error was less than 0.08 nm. By way of the selection of the optimum length of the Er-doped fiber and the introduction of the double isolators, the signal to noise ratio was improved. As a result, the maximum output power of the laser was 4.28 mW, while the stability of the power was 0.03 dB, and slope efficiency was 7.3%.