Spectral beam combination of two Er³⁺/Yb³⁺ co-doped double-clad fiber (EYDF) lasers were experimentally studied through an outer resonator with a blazed grating placed in it. The outer resonator was formed by two dichroic mirrors and a partial reflector. Two EYDFs with different lengths were used as the gain element. A transform lens were employed to locate the output ends of the EYDFs in term of their incidence angle on surface of the blazed grating. The blazed grating was used to select the operating modes of the two EYDF lasers. The wavelength characteristics of a single EYDF laser were tuned experimentally. Stable output of single mode laser was achieved from 1532 nm to 1568 nm. The tunable range was about 36 nm and the 3 dB line width of the output lasers were all less then 0.08 nm. The output powers of the two EYDFs with lengths of 6 m and 8 m respectively were spectrally combined together. The combined output power of 480 mW was achieved on condition that the maximum pump powers coupled into the two fibers were 2.6 W and 4 W,respectively.