We investigated seasonal variations in dissolved organic carbon (DOC) and humic-like fluorescent dissolved organic matter (FDOM<sub>H</sub>) in the Yellow Sea and East China Sea to better understand the factors shaping dissolved organic matter (DOM) dynamics in continental shelf waters. Multi-year observations revealed that DOC concentrations increased with Radium based water residence time, whereas FDOM<sub>H</sub> showed no corresponding accumulation across seasons. This contrasting behavior was particularly evident during summer, when strong solar radiation may promote preferential degradation of photo-labile FDOM<sub>H</sub>, while a relatively more photo-resistant DOC remains in shelf waters, indicating a seasonal decoupling between DOC and FDOM<sub>H</sub>. The persistent increase in DOC with water residence time suggests that a fraction of DOC can accumulate in shelf waters despite ongoing degradation processes. Based on the observed relationship between DOC and water residence time, we estimated a net DOC accumulation flux of 1.1±0.2 Tg C yr<sup>-1</sup>, comparable in magnitude to annual riverine DOC inputs in this region. Our findings highlight the contrasting dynamics of DOC and FDOM<sub>H</sub> and suggest that prolonged water residence and selective DOM transformation may contribute to DOC persistence in continental shelf waters, potentially supporting the export of persistent DOC to the open ocean.