在這份論文中,我們研究投影空間上的Stiefel-Whitney 特徵類,並發現一些計算上的技巧。將之應用到上面,我們可以呈現出投影空間上正切叢的平凡性的必要條件。 In this thesis, we study the Stiefel-Whitney classes of projective space, and develope some calculation technique. As an application, we present the necessary condition for the triviality of the tangent bundle of the projective space.