AlN thin films with small surface roughness and preferential orientation(100) have been deposited on Si(100) substrates by RF magnetron sputtering.In order to enhance the quality,effects of paramters under conditions annealed at high temperature and finished with N2 were studied.The results show that the AlN(100) film is easily formed at high sputtering pressure,but defect such as roughness takes place at the same time.On this occasion,annealing treatment will be helpful.The AlN(100) orientation is also increased with the decreae of proportion of N2.Meanwhile,the films contain Al.In this case,the experiment finished with N2 will be better.The influence of preferential orientation of AlN thin film from energy and the mean free path of sputtering particles are also discussed.