A stable multiwavelength semiconductor amplifier (SOA) fiber laser using a nonlinear fiber loop mirror (NOLM) and a Lyot–Sagnac loop mirror is presented and experimentally demonstrated. The Lyot–Sagnac loop mirror serves as a wavelength selection device, and the wavelength spacing is controlled by the length of polarization-maintained fiber (PMF). The NOLM serves as a power equalizer to achieve power equalization and improve stability. Moreover, the NOLM can also suppress the mode competition effect within homogenous broadening linewidth of SOA. Multiwavelength output with power equality has been achieved at room temperature, with no obvious power fluctuation. The number of lasing lines is 31 within the 10-dB bandwidth, and the wavelength spacing is 0.63 nm. In addition, the average optical signal-to-noise ratio is up to 25.15 dB. Finally, narrower wavelength spacing is obtained by increasing the length of the PMF.