In this paper, we consider n-dimensional compact Willmore hypersurface in a unit sphere. We prove a pinching theorem of ρ 2 , which is defined as ρ 2 = S - n H 2 , for n-dimensional compact Willmore hypersurface with constant mean curvature and constant scalar curvature, where H denotes the mean curvature and S the squared norm of the second fundamental form of this hypersurface.