A tunable S-band fiber ring laser is demonstrated, and the dependence of output power’s on the lasing wavelength and the pump power are experimentally researched. Stable output is obtained with the tuning range of 1482.73～1520.75 nm, the 3 dB bandwidth narrower than 0.03 nm and pump power of 113 mW by tuning an all-fiber tunable Fabry-Pérot filter. In the range of 1487.70～1520.75 nm, the output power exceeds 5 dBm and the side mode suppression ratio (SMSR) is larger than 60 dB. A maximal output power of 7.11 dBm is achieved at 1499.02 nm, together with a fluctuation below 0.04 dB during 900 s.