In order to rationally utilize Scomber japonicus resources and determine their replenishment law, the relationship between age, egg size, and fecundity of Scomber japonicus was studied. Reproductive population samples of Scomber japonicus collected in the central East China Sea in March or April 2021 were used. The results showed that the reproductive population of female Scomber japonicas consisted of 1+ –5+ years old, and the dominant age of 1+ and 2+ made up 68.54%. According to logistic equation fitting, the fork length of 50% sexual maturity was 256.98 mm. Independent samples T-test results showed that there was an extremely significant positive correlation between gonad development and egg size (P＜0.001). There was an extremely significant difference in egg size between the elder age group (3+ –5+ years old) and the younger age group (1+ –2+ years old; P＜0.001). The average absolute fecundity of Scomber japonicas was (358202.06±185914.39) grain/ind; the average relative fecundity in fork length was (1101.70±492.21) grain/mm; and the average relative fecundity in body weight was (881.13±311.46) grain/g. The absolute fecundity and relative fecundity in fork length increased with age, showing extremely significant positive correlations (P＜0.001). There was a significant positive correlation between relative fertility in body weight and age (P=0.017＜0.05). Regression analysis showed that the relationship between the three fertility indices and age was a power function. The absolute fertility contribution rate decreased with the increase of age, and with increasing age, the annual increase of absolute fecundity decreased continuously and then rebounded slightly at 5+ years old. Although elder Scomber japonicus produced higher egg quality and had higher fecundity, due to the small number of elder individuals, the contribution rate of absolute fecundity is smaller than that of younger fish. In formulating the management and protection measures of Scomber japonicus resources, the protection of elder Scomber japonicus should receive special attention.