1. Since the exploitation of spawning stock of the filefish (Navo-don Septentrionalis Giinther), the variations of its body length, body weight and agecomposition were obvious. The individuals of the stock were big in the years of 1974-1976 and 1981-1983, but small in 1977-1980 and 1984 and smaller in 1985 with carlysexual maturation which showed the declination of the resource. 2. The sex ratio of the fish veried in different seasons. The proportion of malereached to the highest level in spawning period and second in over-wiriter seasonwhile nearly equal to female in feeding season. 3. The spawning ground of filefish covers a wide area from 25°30' N to 30°00'N and 122°00'E to 126°30'E according to the distribution of the spawners, hatchedlarvae and juveniles and catch in spawning season, the area mainly covered from25°45'N to 27°00'N and 122°00'E to 123°30'E. 4. The spawning season of the fish starts from the end of March to the last ten-day of May, the peak period in the middle and last ten days of April. 5. The spewning time of the fish were mainly from 23 p. m. to l1 a. m. nextmorning based on the daily change of the propotions of the ovary stage V_A and V_B. 6. By comparing between the experiment in laboratory the adhesion of the artif-icial inseminated eggs and the natural spawning ground, it showed that gravels, she-lls, seaweeds. sponges and corals were the excellent subetrates for the adhesion ofeggs.