Abstract: Thirteen surface sediments and one sediment core were collected from the west Daya Bay (WDB). Biogenic silica (BSi) contents (SiO₂%) in the sediments were measured using a single time digestion technique with 2.0 mol/dm³ Na₂CO₃ solution and the flow-injection molybdate-blue spectrophotometric method. BSi contents in surface and the core sediments were in the range of 0.69%-2.02% and 1.24%-2.05%, with mean values of 1.42% and 1.60%, respectively. As results, BSi contents in the WDB were basically at the similar level as those of other coastal areas of the South China Sea. The profiles of BSi contents, loss on ignition, total organic carbon (TOC) and other factors in the sediment core dated with ²¹⁰Pb_ex method, were analyzed to reveal the impacts of marine environmental change of the WDB in recent 100 years. The marine environment change in WDB was aggravated due to the aquaculture, agricultural and industrial development and the other human activities since 1980s, especially the commercial operation of Daya Bay Nuclear Power Plant in 1990s.