Abstract: In order to obtain a multiwavelength and single longitudinal mode Brillouin fiber laser, an erbium-doped fiber amplifier was placed outside of an about 10m passive optical cavity. Each order Brillouin laser was fed back to the erbium-doped fiber amplifier to amplify again through the coupler. And then, it was used as pumping laser for the next order Brillouin laser to produce multi-order laser Brillouin laser. After theoretical analysis and experimental verification, the result shows that more than seven orders of Stokes signals are observed in the multi-wavelength single-mode fiber Brillouin laser under the condition of current output power of the erbium-doped fiber amplifier. The study will have very wide range of applications in optical generations of microwave, dense wavelength division multiplexing, optical inertial rotation sensor, ultra high precision spectral analysis and so on.