Electron-beam irradiation (EBI) was used to remove phenol in aqueous solution. The removal -efficiencies of phenol were determined, and their relationships with the initial phenol concentration, absorbed dose, and electron-beam energy were investigated. The EBI was conducted in air with absorbed doses from 40 to 120 kGy under 0.3, 1, and 2 MeV electron beams. G-values were introduced to evaluate the removal of phenol quantitatively and were higher at an absorbed dose of 40 kGy than at 80 or 120 kGy. Dose constants (K) were found to depend on the absorbed dose and initial phenol concentration and used to calculate the optimum doses required for 90% (D-0.9) and 50% (D-0.5) removal of phenol. The reduction of the biochemical oxygen demand (BOD5), chemical oxygen demand (CODCr), and total organic carbon (TOC) via EBI indicated organic degradation upon irradiation. The EBI process was combined with activated carbon fiber (ACF) adsorption to improve the CODCr removal efficiency. The optimum ACF doses were 0.5, 1.0, and 1.33 g L-1 with 3, 6, and 6 h contact times for the 20, 50, and 100 mg L-1 phenol solutions, respectively. The combination of EBI with ACF improved the CODCr removal efficiency, even in the more concentrated phenol solution. EBI may be a promising pretreatment process for purifying highly concentrated wastewater.