In order to understand electronic properties of topological films, electronic structures of close-packed planes(0115) thin films from one to five layers of Sb2Te3 and Bi2Te2Se were systemic investigated by first-principle method based on the density functional theory. It was found that at G point the gap width tend to decrease as the increasing of Sb2Te3 (0115) film layers. The metallic state emerges when the layer of the Sb2Te3 (0115) film increases to 5.The similar characters of the electronic structures were found in Bi2Te2Se (0115) film.As the increasing of thickness, the energy gap at G point decreases gradually and the film displays metallic behavior.Our results show that as the increase of film layers both the Sb2Te3 and Bi2Te2Se film lost the insulativity of bulk materials but show gapless metallic surface states of topological insulator.

topological insulator; electronic structures; metallic states; first-principle