Abstract: By analyzing the safety classification for the systems and functions of nuclear power plants based on the general design requirements for nuclear power plants,especially the requirement of availability and reliability of I&C systems,the characteristics of modern DCS technology and I&C products currently applied in nuclear power field are interpreted.According to the requirements on the safety operation of nu-clear power plants and the regulations for safety audit,the effect of different safety classifications on DCS design in nuclear power plants is analyzed,by considering the actual design process of different DCS solutions in the nuclear power plants under construction.