Hydrophilic Iodized X-ray contrast medias (ICM) are difficult to separate from water. Here, a novel porous biochar (MBC) with a high specific surface area (1435.1 m2 g−1) was prepared by one-step pyrolysis, which showed excellent adsorption capacity for Iodized X-ray contrast media, including diatrizoic acid (95.1 mg g-1), iohexol (297.8 mg g-1), and iopamidol (298.9 mg g-1). The optimal pyrolysis temperature for MBC was 700 ℃, and the ratio of sodium hydroxide to sodium carbonate was 1:3. Adsorption kinetic was well fitted by the pseudo-second-order model. Adsorption isotherm was best fitted to the Freundlich model. Adsorption thermodynamics suggested that ICM adsorption was spontaneous and endothermic. Material characterizations demonstrated that good adsorption performance of MBC for ICM mainly depended on pore filling, π-π interaction. The density functional theory (DFT) showed that H-bonding between oxygen-containing functional groups on MBC and ICM further promoted adsorption. Recycling experiments showed that MBC had good reusability. The study indicated that one-step pyrolysis synthesis of alkaline substance pretreatment biochar could be a promising adsorbent for water purification.