On the basis of the molecular mechanics method, using a minimized conformational strain energy calculation, several models have been proposed for chains with six repeat units of aniline. First, a model of a single isolated polyaniline chain is set up. Second, according to the interaction between the two adjacent polyaniline chains, a monolayer film model of parallel chains is presented. Third, a model of double layers of polyaniline chains is presented based on the interaction among three chains located in the different layers. Polyaniline film doped with perchlorate was investigated by a scanning tunneling microscope (STM). STM data are basically in agreement with the above molecular mechanics calculated models.