Magnetic　properties　and　magnetization　processes　of　Co　nanowire　arrays　with　various　packing　densities　are　investigated　by　means　of　object-oriented　micromagnetic　framework　(OOMMF)　software　package　with　finite　difference　micromagnetic　simulations.　The　packing　density　of　nanowires　is　changed　with　the　diameter,　number　of　nanowires　and　center-to-center　spacing　between　the　wires.　The　magnetization　reversal　mechanism　and　squareness　of　the　hysteresis　loops　of　the　nanowire　arrays　are　very　sensitive　to　the　packing　density　of　nanowires.　Clear　steps　and　plateaux　on　the　demagnetization　are　visible,　which　turns　out　that　dipolar　interactions　among　the　wires　have　a　significant　influence　on　switching　field.