Abstract: The influences of the microstructu re of casting strip on the microstructure and magnetic pro-perties of sintered NdFeB magnets we re investigated.The microstructures of the casting strip and sintered magnet were examined by Scanning Ele ctronic Microscope.The experiment al results show that when the cooling speed is too high,the thickness of the columnar plate of the main phase decreases and the over-small isometric grains appear on the cooling surface,both of the above re sult in the solid-solid sintering,unusually grain growing of the main phase(2:14:1)during the sintering process and decreasing the hard magnetic properties of the magnet.W hen the cooling speed is suitable,the main phase grain of casting strip possesses the uniform columnar plate structure with thickness of 3~5μm separated by Nd-rich phase thin layer,which can be used to prepare the high performance sintered magnets.The magnetic properties of sintered NdFeB magnets prepared by the optimum process are listed as follows:B_r=1.44T,_j H_c=877KA/m,(BH)_max=398kJ/m³ (50MGOe).