The recent discovery of the iron arsenide family of layered superconductors RFeAsO1-xFx and AFe2As2 with transition temperature up to 52K has generated tremendous interest as the first high-Tc materials outside the well-known domain of copper oxides. Following our recent observation on MERLIN of a resonant spin excitation in polycrystalline Ba0.6K0.4Fe2As2, we propose to undertake a detailed investigation of the spin dynamics on the single crystal of Ba0.6K0.4Fe2As2.