Antarctic krill (Euphasia superba Dana)is a key organism of the Antarctic marine ecosystem and a potential fishery resoure. Its ecology was the major biologial project in the First Chinese Antarctic Expedition (1985). Acoustic observations and IKMT tows were madecin waters north and west of Antarctic Peninsula .Environmental factors were also observed. Analyses of the population structure, i.e. the sex percentage distribution and other data obtained show that among the 3,640 individuals of determinable sex, only 38.1 % were males and that the larger the body length the smaller the percentage of males,for example, male percentage dropped to 8.3% for size group > 55 mm. The population’s relations to environmental factors are also discussed. Its ecology was the major biologial project in the First Chinese Antarctic Expedition (1985). Acoustic observations and IKMT tows were madecin waters north and west of Antarctic Peninsula. Environmental factors were also observed. Analyzes of the population structure, ie the sex percentage distribution and other data obtained show that among the 3,640 individuals of determinable sex, only 38.1% were males and that the larger the body length the smaller the percentage of males, for example, male percentage dropped to 8.3% for size group> 55 mm. The population’s relations to environmental factors are also discussed.