In this paper, we first give several comparison theorems and their applications in Finsler geometry. Moreover, by means of the Hessian comparison theorems of a real Finsler manifold, Cartan connection, radial flag curvature and tangent curvature, we give Wu’s theorem on a strongly convex weakly Kähler Finsler manifold with a pole. Finally, by using the complex Rund connection and definition of radial flag curvature on a strongly pseudoconvex complex Finsler manifold, we further discuss Wu’s theorem on a strongly convex Kähler Finsler manifold.