Abstract: Wollastonite-sodium silicate-biochar composite material (Ca-Si-C) was prepared by calcination with wollastonite as the matrix material and adding a certain amount of rape straw and sodium silicate. And then the Ca-Si-C was applied to the improvement of acidic yellow soil. The optimum preparation conditions of the composite materials is as follows∶ the mass ratio of wollastonite, rape rod, sodium silicate is 7∶1∶2, the mixture calcines in 600 ℃and muffle furnace for 1.5 h. The results of XRD, IR and SEM show that Ca-Si-C composite loaded with biochar has more surface pores and contains functional groups such as -OH, C≡C, -COOH and C-O. When 2% Ca-Si-C is applied to yellow soil with pH value 4.7, the initial pH value of the soil increases by 1.4 units compared with the control, and the acid damage capacity increases by 11.5 mmol/kg, the dissolution of sodium and potassium in soil increases, the dissolution of calcium, magnesium and aluminum decreases, the intersection point of soil acid buffer curve and aluminum ion dissolution curve increases from pH value 3.5 to 4.1. The Ca-Si-C has a good application prospect in acid soil improvement.