In order to explore the growth regularity of Scomber japonicus in Northwest Pacific Ocean, 210 samples collected by the "Songhang" from 2021 to 2022 used landmarks based on geometric morphometrics.Compared with other methods, the use of landmark methods can effectively reveal the phenotypic diversity of fish, reflect the changes in fish at different stages, and explore their individual growth regularity.The results showed that there were significant differences in the external morphology of S.japonicus across different fork length groups. Both principal component analysis and multivariate analysis of covariance showed that S. japonicus with smaller fork length had more distinct zones, with overlapping zones among the three different fork length groups. Different fork length groups had the same growth regularities.The growth rate of S.japonicus gradually decreased with increasing fork length. The thin-plate spline indicates that the smaller the fork length of S.japonicus, the smaller their abdomen and tail. The morphology of S.japonicus changes with the change of fork length. The conclusion is that the morphology of S.japonicus gradually changes with increasing fork length in Northwest Pacific Ocean.