The TPD technique was used to investigate the desorption behaviour of methanol and acetonitrile on the Cr/MgO catalyst prepared by an impregnation method. Catalytic properties of the Cr/MgO catalysts for acrylonitrile synthesis from acetonitrile and methanol were also studied. The catalytic activities are related to the dissociative desorption temperature of CH3OH or CH3CN on the catalysts.