The invention discloses a precisely tunable Brillouin multi-wavelength fiber laser. A ring resonant cavity is connected between a laser pumping source A and a multi-wavelength generation cavity. The ring resonant cavity is internally provided with a Lio filter used for tuning the laser wavelength. The multi-wavelength generation cavity is internally provided with an MOPA amplification structure for increasing input light power. The MOPA amplification structure provides gain to a high nonlinear fiber and amplifies the laser inputted to the high nonlinear fiber and the laser outputted by the high nonlinear fiber so that the high nonlinear fiber is excited to generate more stages of stokes light and output more wavelength. The inputted laser is tuned through the Lio filter so that precise tuning within the range of few tens of nanometers through temperature can be realized.