Abstract: To identify the content and distribution characteristics of detrital and clay minerals in surface sediments of Sanmen Bay, Zhejiang, East China, where 25 surface sediments, 5 river sediments, and 2 tidal flat sediments were collected. Detrital mineral grains in size of 63～125 μm and clay mineral particles of < 2 μm were analyzed, from which 27 heavy minerals and 11 light minerals were identified. Among heavy minerals, metal minerals, epidote, rock debris, hornblende, schistose mineral accounted for 93.0%; and among light minerals, 81.1% were rock debris, plagioclase, quartz, and flaky minerals. Clay minerals were dominated by illite (61.1%), followed by chlorite (9.3%), kaolinite (15.8%), and a small amount of smectite (3.8%). According to Q-type clustering, the sediments in Sanmen Bay could be divided into estuary mineral area (I), tidal channel mineral area (II), and shallow underwater plain mineral area (III). The mineral provenance analysis showed that fine-grained sediments in the area are mainly from the Yangtze River and are affected by the input of coastal rivers. However, the influence of rivers is very limited as clay mineral pattern dominated by illite has not been changed. The coarse-grained sediments are mainly affected by inner shelf sediments and coastal rivers sediments. The input of coastal rivers increased the content of rock debris and epidote in the study area. In addition, the areas near the bedrock coast in the study area were also affected by some bedrock weathering inputs.