The nuclear island of a new nuclear power plant is designed according to the standard of a foreign country. The material used in equipments,components and structures of the nuclear island shall conform to ASTM,ASME or other codes and standards. During the construction of the subject project,in order to lower the construction cost and shorten the procurement period,some metal materials procured from domestic manufacturer brought material substitution into being,for example,in some cases,some American standard materials were substituted by Chinese standard materials,or other American ones. This paper outlines the material substit-ution issue during the construction of the new nuclear power project. It describes the causes,purposes and requested principles for material substitution,including performance equivalence,code and specification permission,and additional design coordination measures in detail. It also describes the classification,enumeration and analysis of typical cases in regards to material substitution. Besides,based on the method and sharing pointed in this paper,the standardized material substitution process can be formed in nuclear power project construction which can provide reference for material substitution in the acquisition of similar technology or the export of projects.