A stable, tunable single-longitudinal-mode erbium-doped fiber laser (EDFL) with multiple ring cavities (MRC) has been proposed. The MRC consists of two active ring-cavities and two passive subring cavities. The fiber Fabry-Pérot tunable filter and optical grating filter are combined with MRC for mode selection. The output wavelength is tunable from 1528 to 1565 nm over the wide tuning range, the side-mode suppression ration (SMSR) is beyond 44.53 dB ,the maximum SMSR value is up to 51.18 dB around 1554 nm, and the output power is -8.84 dBm in the operating range. With the MRC configuration, the ring laser output is stable, the central wavelength variation is bellow 0.02 nm and the output power fluctuation is less than 0.04 dBm in 18 min, a wavelength-tunable EDFL with stabilized single-longitudinal mode is achieved.