  We consider a vector bundle $E$ over a compact Riemannian manifold
$M$=$M^{n}$,$n\geq 4$,and $A$ is a Yang-Mills connection with $L^{\frac{n}{2}}$
curvature $F_{A}$ on $E$.Then we prove a mean value inequality for the density
$|F_{A}|^{\frac{n}{2}}$.This inequality give rise to an energy concentrate
principle for sequences of solutions that have bounded energy.We also proof
that the energy must be bounded from below by some positive constant unless $E$
is a flat bundle.
