Biochemical and morphological parameters of laboratory-reared developing eggs and larvae of bastard halibut (Paralichthys olivaceus) were measured for oxygen uptake, ammonia excretion, contents of free amino acids (FAA), fatty acids (FA) and accumulated ammonium, and volume of yolk-sac and oil globule at(17.4士0.3)℃。 The bastard halibut had an obvious ammonium cumulation during its egg developmental stage. When hatching, the cumulated ammonia were released. Free amino acids (FAA) acted as the most important energy source during the egg developmental stage, and after hatching fatty acids (FA) of neutral lipids in the oil globule was used as the main energy substrate. Before start-feeding, protein began to supply energy base to some extent. Based on our results and accumulated information, it is concluded that the most important energy source has species-specialty in fish developmental biology and its bioenergetics and further research on this theme is urgent for interpretation of early life history pattern during recruitment of marine fishes.