Hot electron (HE) produced by the localized surface plasmon resonance (LSPR) of metal nanoparticle has been receiving significant attention in the photocatalyst community. In this study, we investigate the effects of surface defects of atomic size on the generation of HE of gold nanocube through discrete dipole approximation (DDA) calculation. The cubic-shaped structure is considered to investigate the sole influences of defects on HE generation, where the plasmon resonance direction is a key factor. More interestingly, when the edge site is doped with silver, generation and lifetime of HEs are enhanced. For a 12 nm length gold nanocube doped with only a single-atomic-layer of silver (50% doping concentration), absorption intensity at peak wavelength and total dephasing time are enhanced by 6.5 % and 11.2 %, respectively. This is a promising result for improving the performance of plasmon-mediated photocatalyst using HEs compared to conventional methods, which are tunable LSPR intensity and wavelength through size, structure shape, plasmon coupling and ambient medium.