The American shad, , is an economically and ecologically valuable anadromous herring native to the Atlantic coast of North America, which was introduced into China as an alternative species to the Chinese shad (because of the latter's near extinction), and is considered as an emerging aquaculture species in China. However, the high mortality rate in the early stage of development, particularly after ingestion of exogenous food, has seriously restricted the development of the industry. Therefore, food selection during seed rearing has important significance. In the present study, the effect of different diets on growth performance, survival, digestive enzyme activity, immune response, and body fatty acid composition in larval American shad were assessed. Larvae of American shad, 10 d after hatching, were reared with different diets ( and micro diet), in triplicate, for 30 d cultivation. The survival and growth performance (survival rate, total length, body weight, and specific growth rate) in the mixed feeding group were significantly better than those in the other two groups during the studied period (<0.05). This may be attributable to the difficulty in digesting micro diets during the early experiment stage and the deficiency of essential fatty acids in , particularly the deficiency of n-3 highly unsaturated fatty acids (n-3HUFA) and docosahexaenoic acid (DHA). There were no obvious differences between the micro diet group and group; however, the survival and growth performance of the micro diet group during the 20 d-30 d period were better than those in the <0.05). This may be because larval fish can digest and absorb micro diets efficiently during this period; moreover, micro diets have a better nutrient content. There were no significant differences in the pepsin and amylase activities among all groups, whereas the activities of trypsin, chymotrypsin, and lipase in the group were significantly lower than those in the other two groups (<0.05). Furthermore, chymotrypsin and lipase activities in the micro diet group were significantly higher than those in the mixed feeding group (<0.05). This indicates that fish larvae could digest micro diets efficiently at the end of experiment, and the addition of micro diets can improve digestive enzyme activities and digestion ability to a certain extent. There was no significant difference in the alkaline phosphatase and superoxide dismutase activities among all groups. The highest activities of catalase (CAT) and lysozyme (LZM) were recorded in the micro diet group, and the activities in this group were significantly higher than those in the <0.05). There was a certain correlation between the survival performance during the 20-30 d period and the activities of CAT and LZM. The mortality in the micro diet group and mixed feeding group remained stable, whereas that in the group continued to decline during this period. This indicates that the addition of micro diets may enhance the non-specific immune response of larval fish. The fatty acid composition of fish larvae was affected considerably by the fatty acid composition of diets. Due to the higher content of essential fatty acids in micro diets, the contents of n-3 HUFA and DHA in the mixed feeding group and micro diet group were significantly higher than those in the <0.05). The experimental results indicate that different diets have an obvious influence on the growth performance, survival, digestive enzyme activity, immune response, and body fatty acid composition of larval American shad. This preliminary analysis showed that mixed feeding with and micro diets before 20 d and full conversion to feeding with micro diets after 20 d can reduce costs and improve production efficiency.