We studied the oxygen effects in the model reaction of methanol with acetonitrile to acrylonitrile over MgO (basic metal oxide) doped with K or Mn. In N2 atmosphere, the doping of K or Mn on MgO enhanced the catalytic activity of MgO resulting in the increase of acetonitrile conversion. In case of Mn-doped MgO, acrylonitrile, the target material, was the main product. Whereas, in case of K-doped MgO, propionitrile formed by further hydrogenation of acrylonitrile was the main product. When oxygen was introduced in the reaction stream, both acetonitrile conversion and acrylonitrile selectivity were remarkably increased over K-doped MgO. Oxygen facilliated the oxidation of methanol to formaldehyde, the reaction intermidiate, and prevented the hydrogenation of acrylonitrile to propionitrile over K-doped MgO. However, introduced oxygen showed a negative effect on Mn-doped MgO resulting in no formation of acrylonitrile due to side reactions.