This report investigated the hydrogen transfer effect and reaction mechanism for HCN hydrolysis by IL ([Bmim](+)[CuCl3](-)). Meanwhile, the influence of preferential break of O-H and C-H bonds in hydrolysis of HCN was investigated. The detailed reaction mechanisms were investigated by theoretical calculations. The results indicated that the formation of complex (HCN-H2O) was an exothermic process and the process was caused by van der Waals forces. The controlling step for HCN hydrolysis was attributed to the migration of H from C-H to N-H bond. The migration of H atom from C-H bond to N-H bond under C-NH structure was easier than that under C-NH2 structure. H2O was firstly adsorbed with IL and then reacted with HCN. The addition of IL enhanced the adsorption effect among reactant molecules by changing the interaction from van der Waals forces to chemical bond effect. IL also decreased the maximum reaction energy barrier by changing H atom migration and exchange actions among IL, HCN and H2O molecules. In general, ionic liquid is a kind promising catalyst for HCN hydrolysis in industrial application.