Abstract: In order to study the effect of coconut shell biochar (CSB) and Fe-Mn modified coconut shell biochar (FM-CSB) on passivation and accumulation of Cd by rice in Cd contaminated soil, an outdoor rice pot experiment was conducted by addition of 0.5% CSB and 0.05%, 0.1%, 0.2%, 0.5% Fe-Mn modified coconut shell biochar (FM-CSB) to the southern acid-contaminated paddy soil. The changes in soil pH, Cd speciation and content in various parts of rice in the treatment group and control group were compared. The results showed that addition of CSB and FM-CSB could increase soil pH, especially at applied amount of FM-CSB higher than 0.1% (P < 0.05). And the best treatment was achieved when 0.5% FM-CSB was added. Compared with CK, application of both CSB and FM-CSB could reduce the content of weak acid soluble Cd in soil along with the prolongation of rice growth period, but increase the content of reducible Cd, oxidizable Cd and residual Cd. The addition of 0.5% FM-CSB resulted in the highest acid-soluble Cd reduction in soil. Cd content in various parts of rice was gradually decreased with the increase of FM-CSB content and the application of 0.5% FM-CSB resulted in the highest Cd reduction in soil with 48.66%, 54.64%, 45.11%, 31.64% and 48.94% decrease in Cd content in rice root, stem, leaf, shell and brown rice, respectively, along with 39.33% increases in rice yield. When CSB and FM-CSB were applied at the same amount of 0.5%, FM-CSB resulted in significant lower Cd content than that of CSB in the rice. Our studies show that the application of 0.5% CSB and 0.05%-0.5% FM-CSB can passivate Cd in soil and reduce the absorption of Cd in rice, and FM-CSB has better passivation effect than CSB on Cd. The research results indicate that FM-CSB could stabilize Cd in soil and reduce the accumulation of Cd in various parts of rice.