Abstract: The performance of multiwavelength Yb-doped double-clad fiber lasers(DCFL) is analyzed based on a Fabry-Perot(F-P) flter,and the wavelength dependence of reflectivity of dichroic mirror in the filter has been taken into account.It is found that the reflectivity of DCF facets and dirchroic mirror can obviously influence the performance,and there is an optimal value of the reflectivity of DCF facets.Using this optimal value,satisfying output power and extinction-ratio can be achieved.And high pump power will improve the output power and extinction-ratio.By controlling the length of F-P filter,the multiwavelength number can be adjusted.