Sediment oxygen consumption (SOC) is an important parameter of marine sediments and an important characterization parameter of the rate of organic carbon mineralization in seafloor sediments, and the study of SOC can help us to understand the carbon cycling process in the whole ocean. As one of the most important and active sites for organic carbon mineralization and burial, marginal seas have received widespread attention and research around the world, but there is still a lack of relevant attention to the Chinese marginal sea region with typical seasonal variations of the marine environment, especially the Yellow Sea and Bohai Sea. In this paper, the intact core incubation was used to study the SOC in the Yellow Sea and Bohai Sea in April, July and October 2022, and the results showed that the rates of SOC ranged from 7.11 mmol/(m²·d) to 17.33 mmol/(m²·d). There was no significant difference between the SOC of the Yellow Sea and the Bohai Sea in spring (ANOVA, p > 0.05), and the SOC of the Yellow Sea was lower than Bohai Sea in summer (ANOVA, p < 0.01) and autumn (ANOVA, p < 0.01); the SOC of the Yellow Sea was the largest in spring and the smallest in summer, and there was no significant difference between the SOC of the Bohai Sea in summer and autumn, which were significantly higher than that of spring (ANOVA, p < 0.05). Temperature and sediment Chl a concentration were the influencing factors. Meanwhile, the SOC was used to assess the rate of benthic organic carbon mineralization. When compared with the primary productivity, the results indicated that the contribution of benthic organic carbon mineralization to primary productivity in the Bohai Sea ranged from 42.8% to 74.5%, which was one of the key links in the carbon cycle of the Bohai Sea, while the benthic organic carbon mineralization in Yellow Sea plays a less significant role in the carbon cycle of the Yellow Sea carbon cycle than Bohai Sea. This paper systematically studied the SOC in the Yellow Sea and Bohai Sea and its spatial and temporal distribution characteristics, exploring the contribution of organic carbon mineralization to primary productivity in the Yellow Sea and Bohai Sea, which provided theoretical support for the understanding of organic carbon mineralization and burial in the Yellow Sea and Bohai Sea.