Abstract: Effect of solution cooling method on microstructure and properties of 10Ni3MnCuAl plastic mould steel were studied. Results show that 10Ni3MnCuAl steel can obtain the better comprehensive mechanical properties, after heat treatment by solid solution treatment at 880℃ for 12 h, oil cooling, and aging treatment at 530℃ for 40 h. The impact energy is 25.6 J. The microstructure of different heat treatment process was analyzed, the oil cooled microstructure is mainly contain lath martensite, lath bainite and a small amount of residual austenite. The slower cooling rate of furnace cooling will promote the phase boundary carbides precipitate, promote the decomposition of the M/A islands, and then significant deteriorated the impact toughness.