High-performance activated carbons are crucial for adsorbing antibiotics in water environment. In this work, amorphous porous biochars (APBCs) with high specific surface area (935 m2·g-1) were achieved by using sesame straw. Compared with the conventional biochars precursor, sesame straw with the advantages of rich resources and low price is more economical and environmentally friendly. Moreover, KOH and Ca(OH)2 were selected as co-activators, which characterization results revealed that co-activators significantly increased the coarseness of activated carbon surface and enlarged pore structure. In addition, the adsorption mechanism of norfloxacin (NOR), ciprofloxacin (CIP) and enrofloxacin (ENR) on APBCs were further investigated by experiments and density functional theory (DFT) calculations. The results discovered that pseudo second-order kinetics and Sips model followed the adsorption experiment data, implying that the adsorption process was heterogeneous and multilayer. And the interactions between APBCs and antibiotics were electrostatic interaction, hydrogen bond and π-π interaction, which were conducive to chemical adsorption.