The polyimide films were formed by imidizing the polyamic acid long-chain alkylamine (dimethylhexadecylamine) salts (PAAS) films with a thermal treatment up to 300 degrees C for 1 hour, where the polyamic acid alkylamine salt films were formed on mica substrates at various surface pressures of 5 mN/m, and 25 mN/m, respectively, by using Langmuir-Blodgett (LB) method. Atomic Force Microscopy (AFM) has been used to investigate the surface morphology of PAAS and imidized films with a thickness of one monolayer at various surface pressures, where AFM was operated in non-contact mode for the surface morphology of the PAAS and imidized films, and in contact mode for the molecular structure of the imidized films, respectively. It was found that a uniform monolayer of the PAAS film was formed even at the surface pressure of 5 mN/m and the root mean squared (rms) roughness of PAAS films formed at 5 mN/m was slightly higher than that of PAAS films at 25 mN/m, but the rms roughness of the former became slightly lower than that of the latter after the imidization.