The investment casting NCu30-4-2-1 alloy with small batches and more kinds was carried out. The rod with size near finished product and meeting performance requirements were trial-produced by designing the rational investment casting parameters and multi-step temperature-reduction method. Aiming at the problems in low strength

the fracture morphology and micro-element of NCu30-4-2-1 alloy was investigated by scanning electron microscope（SEM） and energy spectrometer（EDS）. The results reveal that the local black spot can be observed in the poor strength sample

which is shrinkage porosities. The oxygen impurity element in the alloy and the developed dendrite are responsible for the shrink defect. Through effective by refining and purifying the alloy by trace master alloy as well as optimizing investment casting parameters

the shrinkage defects can be reduced.