Environmental DNA (eDNA) metabarcoding has emerged as a powerful tool for biodiversity monitoring; however, its applicability in coastal ecological surveys in China requires systematic validation. Focusing on Polychaeta, a dominant group of macrobenthos in China’s seas, this study evaluated the performance and efficacy of eDNA technology in biodiversity assessment. Leveraging a ten-year collection dataset across the intertidal zones of China, we constructed a preliminary reference database for the polychaete fauna of China's seas using molecular tools such as shallow sequencing. Field sampling incorporating both traditional morphological surveys and eDNA collection was conducted in representative intertidal habitats to systematically compare the advantages and limitations of each approach. The preliminary results indicate that sequence annotation against a combined reference database ("Local + Public") significantly improves species detection rates compared to using public databases alone. Furthermore, species composition analysis revealed strong complementarity between eDNA metabarcoding and traditional morphological identification. Integrating both approaches substantially enhances the overall efficiency, accuracy, and comprehensiveness of macrobenthic biodiversity monitoring.