The biogeochemical cycle of the earth surface element silicon (Si) affects the earth environmental changes by changing the global primary productivity and the global carbon cycle. In terrestrial ecosystems, Si mainly exists in rocks (weathering crust), soils, plants, rivers and lakes in the form of dissolved Si (DSi), amorphous Si, cryptocrystalline Si and crystalline Si. The soil DSi mainly consists of two parts:monosilicate (primary DSi) released by slow hydrolysis of silicate mineral weathering process and H₄SiO₄ formed by rapid dissolution of soil biogenic silicon (BSi). With the development of soil, the primary DSi was continuously leaching away. The solubility of soil BSi is twice than silicate minerals, and soil BSi gradually became the hub of Si migration and transformation between lithosphere-pedosphere-biosphere-hydrosphere. For the purpose of revealing the change and its driving mechanism of soil BSi in tropical monsoon climate region, soil samples of representative communities (include tropical monsoon forest, economic forest (rubber forest, eucalyptus forest and mango forest) and crops (banana, sugarcane)) in the Changhua River Basin of Hainan Island were collected in dry season and wet season from 2014 to 2016, respectively. The soil BSi content was measured by thermo-alkali digestion and continuous extraction method and its temporal and spatial differences were analyzed. The results showed that there were differences in soil BSi content among different plant communities in the southwestern Hainan Island, in turn, banana land ((2.38±0.72)mg/g)>tropical monsoon forest ((1.86±1.34) mg/g)>rubber forest ((1.42±0.81) mg/g)>eucalyptus forest ((1.22±0.28) mg/g)>mango forest ((0.98±0.71) mg/g)>sugarcane land ((0.62±0.74) mg/g). Due to the differential absorption of element Si by different plants during the growth process, soil BSi content in the study area varies with the plant community in season:the soil BSi content in the forest community in dry season was higher than that in wet season, however, the soil BSi content in the agricultural herbaceous community (for example, banana and sugarcane) was higher in wet season than that in dry season. Correlation analysis and principal component analysis suggested that the changes of soil BSi content were mainly controlled by the soil mineral chemical weathering, soil organic carbon content, total nitrogen and C/N ratio, implying the coupling driving mechanism of biological factors and abiotic factors on soil BSi pool change in the study area. The averaged soil BSi content (1.43 mg/g) in the southwestern Hainan was lower than that (2.5 mg/g) in the tropical rainforest region. The reason why is that more active microbial activity and stronger erosion of rainfall runoff in the mountain soil during the heat and water period, which is conducive to the migration and transformation of the soil BSi, and is discharged into the South China Sea in the form of dissolved silicon eventually. Clearly, the soil BSi dynamic, to a certain extent, maintains the nutrient composition structure and ensures the virtuous cycle of the South China Sea ecosystem.