In the experiment,laser diodes are used as pump sources,and large-mode-area Er3+Yb3+ co-doped double clad fiber lasers as the gain media.Adopting the structure of external cavity with a Fourier transform lens,blazing grating and outcoupling mirror,spectral beam combining of two Er3+Yb3+ co-doped double clad fiber lasers are achieved.The maximal output power of fiber laser is 520 mW and 545 mW respectively.With the combined beam power of 690 mW is obtained and the combined efficiency is 65% when the diffract...