On the basis of FeSO4 and KMnO4 modified sepiolite(FM-sepiolite), effects of FM-sepiolite and natural sepiolite on soil pH, Sb morphology and the migration law of Sb in soil-pakchoi system were studied with a 50-day pot culture experiment. The pot experiment had 7 treatments including 0.5%, 1.0% and 2.5% natural sepiolite, 0.5%, 1.0% and 2.5% FM-sepiolite and control(CK). The results showed that the FM-sepiolite had a porous structure and higher specific surface area after being modified by FeSO4 and KMnO4. The specific surface area of FM-sepiolite increased 18.11% and the contents of Fe and Mn increased significantly, and which showed with amorphous form. Compared with CK, the soil pH increased after various concentrations of natural sepiolite and FM-sepiolite added. Of them, the treatment with 2.5% FM-sepiolite had the most significant effect. The contents of crystalline iron-aluminum-bound Sb and residue Sb increased with addition of FM-sepiolite, and the reverse was true for soil non-specifically adsorbed and obligately adsorbed Sb, amorphous iron oxides and amorphous Sb. Compared with adding natural sepiolite, the content of non-specifically adsorbed Sb in the soil modified by adding FM-sepiolite decreased by 2.48%-43.31%. The translocation of Sb in the soil-pakchoi system was hindered by the application of the FM-sepiolite and natural sepiolite; and the Sb mass fraction and enrichment coefficient of each part of pakchoi reduced significantly and the mass fractions of Sb in root and stem-leaf decreased by 6.83%-44.26% and 19.51%-59.23%, respectively. Among them, the application of 2.5% FM-sepiolite had the best effect, and the effect of FM-sepiolite was better than that of natural sepiolite with the same application amount. All results showed FM-sepiolite was an effective material of harness of soil polluted by Sb.