Low-cost and efficient activated carbon (AC) was prepared from Typha orientalis via phosphoric acid activation for chloramphenicol (CAP) removal. The adsorption capacity and mechanisms of CAP on AC were investigated. The physicochemical properties of AC were characterized by an N2 adsorption/desorption isotherm, elemental analysis, Boehm’s titration and X-ray photoelectron spectroscopy (XPS). The effects of experimental parameters were investigated to study the adsorption behaviors of CAP on AC, including contact time, initial concentration, ionic strength, and initial pH. AC had a micro-mesoporous structure with a relatively large surface area (794.8 m2/g). The respective contents of acidic and basic functional groups on AC were 2.078 and 0.995 mmol/g. The adsorption kinetic that was well described by a pseudo-second-order rate model implied a chemical controlling step. The adsorption isotherm was well fitted with the Freundlich isotherm model, and the maximum CAP adsorption capacity was 0.424 mmol/g. The ionic strength and pH had minimal effects on CAP adsorption. The dominant CAP adsorption mechanisms on AC were evaluated and attributed to π-π electron-donor-acceptor (EDA) interaction, hydrophobic interaction, in conjunction with hydrogen-bonding interaction. Additionally, AC exhibited an efficient adsorption performance of CAP in a realistic water environment.