Abstract: Using dregs of soy sauce to culture photosynthetic bacteria, the technological conditions such as ratio of materials, water content, thickness of materials, illumination and dryness were optimized. The amino acids in the protein-enriched feed produced by photosynthetic bacteria in dregs of soy sauce were determined and this feed was applied to cultivate fry. The results showed that the content of crude protein in the feed was 21.3%～22.7% when photosynthetic bacteria were cultured under the follewing conditions: a 7∶3 ratio of dregs to bran, a water content of 54%～58%, 7.0～8.5 cm thickness of materials; 5% inoculum, natural illumination and a temperature of 25℃ for 3 days. Compared with the raw material, the content of crude protein and the total amount of amino acids increased by 35% and 20% respectively. The application of this feed to cultivate fry showed that the survival ratio of fry increased, while the size of fry remained small. As a feed source, it could be mixed in proper proportions with other high protein-enriched feed.