Ordered chain orientation of polyimide in Langmuir-Blodgett films is necessary for liquid crystal alignment. In this paper the influence of dipping process on the polyimide chain direction is studied by Monte Carlo method. It is found that the oriented polyimide chain is caused by dipping process and its orientation is almost parallel to the dipping direction. The linearity of the chain depends upon the dipping velocity, which is reinforced by fractal dimension analysis.