Theoretical simulation on the enantioselective cyanation of benzaldehyde over titanium-salicylaldehyde catalysts is performed with B3LYP//ONIOM methods. The calculations predict that the attack of cyanide to adsorbed benzaldehyde is the rate-determining step for the entire reaction. The stereochemistry of the titled reaction might be controlled not only by the attack directions of cyanide to benzaldehyde but also by different coordination modes of benzaldehyde to the chiral catalysts. In addition, to evaluate the accuracy of the employed method, the stereoselectivities of the reactions with five different chiral ligands are theoretically predicted. The theoretical predictions are qualitatively in agreement with experiments, and a linear relationship between calculated Delta DeltaG(double dagger) and experimental ones is obtained, especially for the reactions using the ligands with a single chiral center.