We proposed a modified off-axis spectral beam combining method, based on the concept of selective feedback. A high reflectivity mirror with a fixed width was used to select and couple back the optical modes in the external cavity. The emission power exceeding 20 W with M2 factors of 2.7 × 4.4 in the fast and slow axes was demonstrated. The beam quality of the system was improved by a factor of three to four compared with that of a single emitter, and a high brightness of 190 MW cm-2 str-1 was achieved.