A 4.5 W all-fiber narrow-linewidth two-tone laser based on stimulated Brillouin scattering is established. The wavelength separation of two-tone laser is 0.06 nm. The output power is 4.5 W and the optical conversion efficiency is 50%. Spectral properties, output power properties and coherence of the laser are compared with single-tone fiber laser experimently. Experiment results indicate that the narrow-linewidth two-tone fiber laser has the similar output power properties with the single-tone fiber laser. The visibility of the far-field interference pattern reaches 80%, when the two-tone fiber laser is at the max output power. The narrow-linewidth two-tone fiber laser can be used for coherent beam combination.