A. The most important fatty acids in quantity were C 16:0、C 18:1ω9、C 18:2ω6、C 18:0 and C16:1 in each embryonic development stage. Among the unsaturates (UFA), the utilization of the monounsaturates (MUFA) was higher than that of the polyunsaturates (PUFA). C18:1ω9c was used mainly as an energy source during embryonic development stages. C17:1 and ARA were used mainly as structural substances in embryos. Both EPA and DHA played a crucial role in the development of the circulatory system and the central nervous system during the later embryonic development stages of M. rosenbergii. Among five digestive enzymes determined, enzyme activities of pepsin, tryptase and amylase were relatively high. Enzyme activities of pepsin, tryptase, amylase and cellulase had a change of 'high-low-high', while the enzyme activity of lipase decreased. Gastrula stage was a special stage of embryonic development, which mRNA began to express by embryo and more digestive enzymes were ready to synthesize to ensure thutilization of yolk. Enzyme activities of pepsin, tryptase, amylase and cellulase reached the highest level in zoea stage. The results indicated that variations of biochemical changes and digestive enzyme activities correlated closely with the embryonic development.