Abstract: Polyamic acid was synthesized, and the conditions of forming films on gasliquid interface were discussed. The Langmuir-Blodgett(LB) films of polyamic acid salt and polyimide LB (PILB) films by thermal treatment were obtained. The completeness of removal of amine was confirmed by IR spectrum. In addition, a liquid crystal cell was built using PILB films to align S_A phase liquid crystal. Using polarizing microscope, we confirmed that PILB films without rubbed can align smectic liquid crystal with good results. The affecting factors of forming films and alignment of liquid crystal moleculae on PILB films were also discussed.