Impurity segregation at grain boundary (GB) can significantly affect the mechanical behaviors of polycrystalline metal.The effect of nickel impurity segregated at Cu GB on the deformation mechanism relating to loading direction is comprehensively studied by atomic simulation.The atomic structures and shear responses of Cu Σ9(114) 〈110〉 and Σ9(221)〈110〉 symmetrical tilt grain boundary with different quantities of nickel segregation are analyzed.The results show that multiple accommodative evolutions involving GB gliding,GB shear-coupling migration,and dislocation gliding can be at play,where for the [(s)2(i)] shear of Σ9(114) 〈110〉 the segregated GBs tend to maintain their initial configurations and a segregated GB with a higher impurity concentration is more inclined to be a dislocation emission source while maintaining the high mechanical strength undergone plastic deformation for the [1 (1)(4)] shear of Σ9(221) 〈110〉.It is found that the nickel segregated GB exerts a cohesion enhancement effect on Cu under deformation:strong nickel segregation increases the work of separation of GB,which is proved by the first-principles calculations.