A novel continuously tunable multi-wavelength fiber ring laser is constructed by using semiconductor optical amplifier (SOA) as the gain medium. A Hi-Bi fiber loop mirror (Hi-Bi FLM) is inserted into the cavity as filter. More than 17 stable wavelengths with line-width less than 0.102 nm and more than 25 dB SNR spacing on ITU-grid (100 GHz) are obtained. The output peak power variation of each wavelength is less than 6 dB. These 17 wavelengths can be continuously tuned together within 50 GHz by proper control of the polarization controller of Hi-Bi FLM. The feasibility of using this multiwavelength fiber ring laser in testing the characteristic of erbium-doped fiber amplifier (EDFA) is discussed experimentally.