Abstract: A paddy field experiment was conducted to explore the remediation effect and mechanism of mercapto bentonite (Bent-SH) on Cd contaminated soil. The results showed that Bent-SH had little effect on the physicochemical properties of soils. Compared with the control group, the available Cd in soils was decreased by 48.57% at most. The Bent-SH reduced the migration ability of cadmium in soil and the absorption of Cd by rice and straw, The Cd contents in rice and straw were decrease by 72.73% and 70.97% at most, respectively. The EX-Cd was decreased by 54.17%, while the FMO- and SO-Cd were increased by 117.4% and 75.00% at most, respectively. The Bent-SH addition amounts were extremely significantly negatively correlated with available Cd and Cd in rice and straw, significantly negatively correlated with EX-Cd, but extremely significantly positively correlated with FMO-Cd and SO-Cd. The Bent-SH could reduce the activity and bioavailability of Cd by the conversion of Cd form from EX to FMO and SO, thereby achieving the passivation remediation of Cd contaminated soils.