Organosulfur constitutes the second largest marine sulfur reservoir after sulfate and serves as an important substrate pool for heterotrophic bacteria, yet its relationship with bacterial community structure in productive coastal seas remains poorly constrained. Here, we quantified dissolved organic sulfur (DOS) and particulate organic sulfur (POS) and examined their associations with bacterial communities across 31 stations in the Bohai and Yellow Seas. DOS concentrations ranged from 1.7 to 6.8 µmol L-1 in surface waters and from 0.9 to 5.4 µmol L-1 in bottom waters, whereas POS ranged from 0.3 to 1.7 µmol L-1 and from 0.2 to 1.6 µmol L-1, respectively. These concentrations exceeded previously reported open-ocean values, and the corresponding organic carbon-to-sulfur ratios were substantially lower, indicating sulfur-enriched organic matter in these marginal seas. Minimum organic sulfur inventories were 0.039 ± 0.025 Tg S for POS and 0.300 ± 0.058 Tg S for DOS in the Bohai Sea, and 1.14 ± 0.69 Tg S for POS and 1.91 ± 0.52 Tg S for DOS in the Yellow Sea. Although bacterial communities differed between surface and bottom waters in diversity and network complexity, partial least squares path modeling showed no significant direct association between DOS and bacterial community composition or abundance in either layer. Instead, bacterial patterns were more strongly linked to environmental conditions and bulk organic carbon. These results suggest that coastal organic sulfur can represent a large standing stock while exerting only a limited community-level imprint, likely because bioavailable sulfur substrates occur at much lower concentrations and are used selectively by specific bacterial taxa. This work refines the understanding of organic sulfur-microbial interactions in shelf seas and highlights the need for molecular speciation and isotope tracing of coastal organic sulfur pools.