Relation of optical properties in a uniform fiber Bragg grating(FBG) with its grating parameters and the laser beam engraving conditions is analyzed. The principle and method for designing the uniform FBG used in dense wavelength division multiplexing(DWDM) system is given. By adopting the double exposure technique, with a uniform phase mask and Gaussian laser beam, the uniform FBG used in DWDM system is designed and engraved, whose bandwidth of the main reflection band is about 0.4 nm and 0.7 nm at -5 dB and -25 dB respectively. The principle and method for designing the uniform FBG used in dense beam division multiplexing (DWDM) system is given. The principle and method for designing the uniform FBG used in dense beam division multiplexing (DWDM) system is given. the double exposure technique, with a uniform phase mask and Gaussian laser beam, the uniform FBG used in DWDM system is designed and engraved, whose bandwidth of the main reflection band is about 0.4 nm and 0.7 nm at -5 dB and -25 dB respectively .