We study vector bundles on flag varieties over an algebraically closed field $k$. In the first part, we suppose $G=G_k(d,n)$ $(2\le d\leq n-d)$ to be Grassmannian manifold parameterizing linear subspaces of dimension $d$ in $k^n$, where $k$ is characteristic $p>0$. Let $E$ a uniform bundle $G$ rank $r\le d$. show that either direct sum line or twist pull back universal $H_d$ its dual $H_d^{\vee...