Abstract: This paper describes the application of alloy 690 in PWR nuclear power plants,as well as the main technical requirements and characteristics of alloy 690 tubes of AP1000 Steam Generators.Through different heat treatments and deformation process,this paper also studies the laws between chemical segregation,stable and continuous intergranular carbide precipitation and different process combinations.Test results indicate that the deformation extent and cooling speed after annealing have a great impact on the chemical segregation and the pattern of intergranular carbide precipitation.