The three-dimensional viscous flow near the rotor tip is one of the most important and difficult problems in rotor dynamics. Most of theoretical investigations focused upon the tip flow field problem confined to inviscid analysis. The detailed study of the complex three-dimensional viscous flow near the tip region can play an important role in determining the generated rotor noise, rotor performances, and dynamic loading of the rotor blade. Through solving the boundary layer flow, the present work is to deeply investigate the viscous flow near the rotor tip. The solution of the boundary layer flow at that region is expected to explain many phenomena that arise in rotor dynamic.