To study the biological characteristics of the breeding stocks of Scomber australasicus in the East China Sea, we analyzed the biological characteristics of the breeding stocks of Scomber australasicus, including fork length, body mass, feeding grade, fattening, gonad index, sex ratio, and muscle content, based on 227 Scomber australasicus samples collected in the south-central part of the East China Sea between January and April, 2016— 2023. The results showed that there was no significant difference in the relationship between fork length and body mass between the sexes of the breeding stocks of Scomber australasicus (P＞0.05), and the equation for the relationship between fork length and body mass fitted to both sexes was W=3×10^–6FL^3.2558. January is the overwintering period for Scomber australasicus, and the breeding period is from February to April. The peak spawning period of the Australian mackerel was concentrated in March, and the proportion of mackerel that had already spawned increased by late April. Female mackerel always have a higher gonadal index than male mackerel and less muscle mass than male mackerel, with equal gonadal development. Feeding intensity declined and then increased from the overwintering period to around the breeding period, whereas fattening increased and then declined before returning to pre-breeding levels. Males outnumbered females in early breeding in February, and females outnumbered males in late breeding from March to April. This variation in sex ratio during the breeding period is consistent with a breeding strategy that maximizes generation replenishment and reproductive gain. During the breeding season, the female Scomber australasicus organism allocates more energy to gonadal development than the male, while allocating less energy to muscle, to ensure population continuation. Female Scomber australasicus are more abundant than males during the breeding season, which may be related to the fact that Scomber australasicus is trying to increase the number of offspring to ensure the continuation of the population. The breeding season affects the feeding activity of Scomber australasicus, leading to a decrease in fat content. It was found that female Scomber australasicus outnumbered males in the large-bodied Scomber australasicus population, and that fork length and body weight were slightly higher than in males. However, further research is required to investigate this phenomenon. The biological characteristics of the reproductive stocks of Scomber australasicus in the south-central East China Sea were analyzed to enrich the biological data on the reproductive stocks of Scomber australasicus in the south-central East China Sea, which will provide a basis for the conservation and utilization of Scomber australasicus in the south-central East China Sea.