The present application provides a growth method of aluminum nitride (AlN), including the following steps: providing a substrate; using a metal organic chemical vapor deposition (MOCVD) device to simultaneously supply metal source gas, nitrogen source gas and group VI element source gas to the substrate to form an AlN nucleation layer on the substrate; and using the MOCVD device to simultaneously supply the nitrogen source gas and the metal source gas to the AlN nucleation layer to form an AlN crystalline layer on the AlN nucleation layer.