A method of fabricating dual-wavelength fiber Bragg grating with a uniform phase mask is demonstrated. Theoretical analysis and numerical simulation using matrix method are given. The moving exposing technique is adopted. A good control over the grating's reflectivity and the separation of the two Bragg wavelengths is enabled by adjusting the stretch, the length of the grating, and the exposure. A grating with two equal transmission peak of 19.5 dB is obtained by using this method and the separation of the two Bragg wavelengths is 0.78 nm.