Abstract: The rule and formation mechanism of surface morphology alteration in Inconel 718 alloy irradiated with three different doses were studied. The results indicate that He⁺ ions irradiation would produce nanopores in sample surfaces. The aperture of these nanopores increases with irradiation dose. Besides, He⁺ ion irradiation would break δ phases and lead to continuous sputtering of carbide in sample surface, and the increase of irradiation dose would aggravate these phenomena. The microstress σn between bubbles induces the fracture of adjacent material, and it also promotes the coalescence and growth of bubbles. Moreover, sputtering results in the rupture of bubbles. Therefore, the formation mechanism of nanopores in irradiated Inconel 718 alloy attributes to the combined effects of bubble growth and surface material sputtering.