Grain boundary engineering(GBE)was applied to enhancing the stress corrosion cracking(SCC)resistance of 304 stainless steel.After the GBE treatment,the grain boundary network(GBN)was featured by the highly twinned grain-clusters.The slow strain rate tension(SSRT)tests were used to compare the SCC resistance between the GBE treated and the Non-GBE treated samples in a simulated PWR water.It took longer time for the GBE sample to rupture than the Non-GBE sample.Fracture surface morphology showed that the IGSCC was easier to propagate in the Non-GBE sample than in the GBE sample.This indicated that the GBN has a strong influence on the SCC resistance of the material in the PWR water environment.After the SSRT tests,small cracks with a scale of several tens of microns on sample surfaces were examined by using the EBSD(Electron backscattering diffraction)technique.It is observed that the transgranular micro-cracks initiated preferentially in grains with larger Schmid Factor,and the intergranular micro-cracks preferentially initiated at grain boundaries between two grains with larger difference in Schmid Factors.