In present report, we explored hyperconjugation effects on the site- and bond-selective dissociation processes of cationic ethanol conformers by the use of theoretical methods (including configuration optimizations, natural bond orbital (NBO) analysis, and density of states (DOS) calculations, etc.) and the tunable synchrotron vacuum ultraviolet (SVUV) photoionization mass spectrometry. The dissociative mechanism of ethanol cations, in which hyperconjugative interactions and charge-transfer processes were involved, was proposed. The results reveal C-a-H and C-C bonds are selectively weakened, which arise as a result of the hyperconjugative interactions sigma Ca-H -> p in the trans-conformer and sigma(C-C) -> p p in gauche-conformer after being ionized. As a result, the selective bond cleavages would occur and different fragments were observed.