Silicon(Si)was an essential nutrient element for the growth and development of cereal crops such asrice.Soil pH affected thetransformation and availability ofSi，and there was a significant competitive adsorption effect between soilphosphorus(P)andSi.To investigate the effects of soil acidification and P enrichment onthe availability and mobility of soilSi，P and Si competitive adsorptionexperiment，soil incubation experiment and Si fraction experiment wereconducted.The results showed that the presence of P reduced the amount of Si adsorbed by the soil by 78%-350% when equimolar concentrations of Si and P were added simultaneously in the pH range of 3.5 to6.4.Si sorption wasless than that ofP，soil acidification andP addition reduced Sisorption，and the effect of P addition in reducing soil Si sorption was moresignificant at higherpH(inthe pH range of 3.5 to6.4).Soil acidification decreased the content of movableSi，adsorbedSi，organic Si and Fe/Al/Mn -oxideSi，but increased the content of amorphousSi.The contents of movable Si and adsorbed Si were reduced by 22.47%-54.32%，10.72%-33.40%，respectively.P addition increased the content of movable Si by 4.07%-9.40% and adsorbed Sidecreased by1.19%-3.53%.The dissolution and sorption -desorption processes of soil Si wereregulated bypH，and thereby affected the mobility of soilSi.P enrichment promoted the desorption of soil adsorbedSi，which in turn enhanced themobility of soilSi.