Mathematics descriptions of Dean vortices movements were performed under polar coordinates and Cartesian Coordinates respectively through numerical methods. And on the base of the mathematics description，numerical simulation was carried out to study the characteristics of the Dean vortices from the radial velocity，axial velocity and circulation. The results showed that the radial velocity varied slowly in the curved pipes between the cross-section 15 °and 75 °，while increased significantly in the inlet and outlet of the pipe，and the axial velocity assumed wavy variation in the whole curved pipe，while the circulation assumed parabolic variation as the increment of Dean number.