In this thesis we show an Einstein manifold of dimension n ? 4 with nonnegative isotropic curvature is locally symmetric. At first we show that an Einstein kahler manifold with nonnegative isotropic curvature has constant holomorphic sectional curvature. In continue we focuse on quaternion-kahler manifold and with considering the decomposition R=R 1 +kR 0 for the curvature tensor of a quaternion-kahler manifold we show that R 1 must be identically zero. Finally by means of obtained results we prove the main theorem of this thesis.
