Silicon, the second most abundant element in Earth’s crust, is intricately linked to the global carbon cycle through its biogeochemical processes, playing a pivotal role in regulating atmospheric CO₂ concentrations, marine primary productivity, and coastal eutrophication. Biogenic Silica (BSi), a silicon-containing compound produced by biological metabolism, serves as the primary pathway for silicon removal from the ocean via sedimentary burial. However, the lack of unified standards for BSi determination in China's offshore sediments has impeded data comparability across studies. An extensive evaluation was conducted to assess the effects of key parameters, including pretreatment methods, extractant concentration, temperature, and duration, on the measurement results of BSi. The findings demonstrate that the optimal analytical approach for determining BSi in China’s coastal marine sediments involves extraction with 0.5 mol/L Na₂CO₃ solution at 85 °C for 8 hours, without any preliminary chemical pretreatment. This research compiles BSi content and distribution data from sediments in the Bohai, Yellow, East China, and South China Seas. It calibrates data generated under different pretreatment and extraction conditions against the optimal methodology, and analyzes spatial distribution characteristics and influencing factors. Results indicate that BSi content in China’s offshore sediments ranges from 0.05% to 3.82%, with an increasing trend from north to south, alongside distinct planar and vertical distribution patterns in different sea regions. Key influencing factors include water column primary productivity (particularly diatom productivity), sediment dissolution rates (regulated by temperature, pH, specific surface area, and aluminum content), and human activities (such as nutrient input and hydrodynamic changes). This study provides an improved data foundation and methodological framework for subsequent high-precision marine silicon cycle research, carbon sink assessment, and predictive modeling of coastal ecological evolution in China’s offshore areas, while simultaneously highlighting the urgent necessity for establishing national BSi standard reference materials and standardized analytical protocols.