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First, we introduce the energy-momentum tensor of the spinning particles and use it to derive the Papapetrou's spin equation. In the post-Newtonian approximation method, we expand this tensor to the post-Newtonian order and derive corresponding equations of motion. In the chapter 4,the N spinning particle results are reduced to the case of a binary system. To see how the spin effects come in, the equations of motion, the central position,the total energy and the total angular momentum are evaluated including spin effects. Finally, consider a general elliptical orbit, and obtain the velocities, spin vectors,and position in all three directions One find that, in particular, the velocity and the displacement in the z-direction are non- zero. Only in the post-Newtonian or higher orders, the spin effects cause the binary system to leave the plane of the Newtonian orbit. Most stars possess spin. If we want an accurate result, we can not but consider the spin effects.
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