The present paper deals with the freeding habit of the filefish Navodon septentrionalis (Günther) distributed in the outer region of Dong Hat.There have been examined and analysed 852 samples which were collected from the bottom trawling explorations during the period from January to June in 1974 to 1976. The results may be summarized as follows:1.Naxodon septentrionalis is a kind of omnivorous fish mainly feeding on the planktonic crustaceans as well as mollusca and corals.2.There are two peaks of feeding activity occurring in February to March and May respectively and the valley is in April, probably concerned with breeding activities.3.Thefeeding activity and the food composition of filefish varies in different areas, the southern shoal being the highest, the middle one the second, and the northern shoal the lowest.4.The feeding habit of Navodon septentrionalis also exhibits the phenomenon of diurnal vertical movement.