Abstract: In order to optimize the design of fiber Raman laser,a fiber laser with DCF as gain medium under a simplified model and its output characters are analyzed.Some methods are put forward to optimize the design of fiber lasers.Laser output can be optimized with alterations of fiber length and output coupling coefficient,and the output power can be changed with alteration of pump power.Applying the model to the multi wavelength lasers,four-wavelength lasers have been obtained.