Through establishing a theoretical model of the external optical feedback semiconductor laser and combining the laser rate equation and noise theory, the influences of gain chip parameters and fiber Bragg grating parameters on the frequency noise and relative intensity noise of the laser under different injection current are discussed and optimized in this paper. The simulation results indicated that by changing the injection current and adjusting the size of active region, the structure of fiber Bragg grating and coupling coefficient, the frequency noise of the laser could be decreased about 5×108Hz and the relative intensity noise of the laser could be decreased about 8dB/Hz in theory. The result obtained in this work can provide a theoretical guidance for the experimental study of the external optical feedback laser with low noise and narrow line-width, and it has reference significances to the study of the noise characteristics of other external cavity lasers.