Multi-wavelength narrow linewidth lasers can greatly reduce the cost for light sources used in dense warelength division multi-plexing (DWDM) optical network node equipment. A way to achieve it by an active fiber ring resonator incorporating an optical phase modulator is proposeed. Its output power is stable because there is no mode competition in it. Hundreds of laser wavelengths can be achieved when the frequencies of input laser and radio frequency modulation signal coincide with the frequency of the resonator′s longitudinal mode. The expression of the multi-wavelength laser is derived. Computed results show that the relative total output and the single-wavelength relative output are related to modulation depth of phase modulator and coupling coefficient of the input/output coupler. The coupling coefficient below 0.9 and the phase modulation depth above 2.0 rad benefit stability of output power. Total output and single-wavelength output power can reach several hundreds milliwatt and milliwatt levels. Theoretical analysis and calculations show the linewidth of any laser wavelength in the multi-wavelength laser is about equal to that of input laser when the circulating time inside the resonator is not much larger than coherent time of input laser.