The AlN thin films with preferred orientation were deposited on Si(111) substrates using magnetron reactive sputtering. The effect of sputtering power on surface roughness and structure of the AlN thin films has been investigated. The experimental results indicate that as sputtering power increases, deposited rate also increases, but surface roughness and preferred orientation degree of AlN thin films become bad. Therefore, lower sputtering power should be chosen for preparing AlN thin films of good quality.