In order to understand the variation in population structure of Antarctic krill in the Scotia Sea in winter and to explore the overwintering mechanism of Antarctic krill, using the samples collected randomly from fishery survey from May to August 2017, the population structure of Antarctic krill in the Bransfield Strait and the South Georgia Island was studied. The results indicate that the monthly sex ratios are not significantly different and the proportions of females are higher than those of males, and the sexual maturity stage has no significant difference between months. Overall, female krill remains immature throughout the winter months, with a few exceptions.For male krill, in May, the number of immature male is lower than that of matures, the number of immature male is more than that of matures in June, the proportion of immature males is higher than that of mature males in July, and all individuals are immature in August.For the Bransfield Strait and the South Georgia Island, as a whole, the number of mature krill decreases since the onset of winter,while the number of immature krill increases gradually. Through the comparison to the historical data, it can be seen that the population structure of Antarctic krill significantly varies inter-annually and annually in the Scotia Sea in the winter.