In this paper, biological measurements such as body length and body weight and identification of stomach contents were carried out based on Pacific cod（Gadus macrocephalus）samples captured in the Yellow Sea from 2017 to 2021. Decision tree method was used to analyze 489 stomach contents data to explore the changes of feeding habits with body length and seasons. The results showed that the relative importance index of Crangon affinis and Engraulis japonicus was relatively high in 2017—2021, and the next were Enedrias fangi, Alpheus japonicus and Gobiidae. Its feeding habits vary greatly with seasons, mainly preying on Crangon affinis and Engraulis japonicus in summer and autumn, while its feeding habits are relatively wide and its Shannon-Wiener index is higher in spring and winter, which may be related to the overwintering of most fishery species in the Yellow Sea during spring and winter. In addition, the Pacific cod 's feeding habits change with the growth of its body length. The juveniles mainly feed on crustaceans, while the adults shift to eat Gobiidae, Enedrias fangi, etc. The main reason is that the Pacific cod 's mouth slit becomes larger, its swimming ability becomes stronger, and it has more nutrients to meet the growth requirements. Other Pacific cod individuals were found in the gastric contents, indicating cannibalism. In addition,compared with previous studies, the diet abundance of prey gradually decreased, Euphausia pacifica and Larimichthys polyactis almost did not appear in the stomach, and the importance of Engraulis japonicus gradually decreased, and Gobiidae are becoming more important.