Reflectance anisotropy spectroscopy is a non-contact technique for surface detection. which means through the optical reflection from surface of the substrate measured. Because of its high sensitivity, RAS is used for in real-time control of semiconductor epitaxy. On our study, RAS is used to study the surface characteristics of liquid crystal alignment layer. We used rubbing for polyimide film to achieve alignment purposes. The rubbing strength is determined by adjusting the pile impress and the number of rubbed. We found that the anisotropy spectroscopy will appear after rubbing. And the strength of RA signals changes with photon energy of the probe beam. The pretile angle of the liquid crystal sandwiched in between rubbed PI show certain degree correlation with RA strength. In addition, using surface free energy measurement to explore the relationship with pretilt angle and try to connect three of them. We also tried to measure the reflection signal from the sample back. We found the signal of sample back would decay in UV region and it may be a result of UV absorption in the substrate.