An ultrasonic-assistant fore-modified method was designed to develop the self-functionalized biochar (SFB) with enhanced adsorbability. Characterized by different morphologies, SFB was presenting particular groups of carbon micro-spheres. Possessing ultrahigh surface area of 2368 m2/g, SFB exhibited excellent adsorption capacity (up to 497 mg/g) towards traditional antibiotic. Besides, more functional groups, which played important roles on the solid-liquid interface interaction, posed on the surface of SFB. The removal efficiency of levofloxacin was up to 99.93 % in the competitive system. Adsorption mechanism was analyzed based on the results of FTIR, kinetics, isotherms and competitive adsorption experiments. The chemisorption affinity on the solid-liquid interface was strong enough, which was proved by isotherms, thermodynamics and Kd analyses. Meanwhile, SFB has presented a good resistance against humid acid interference in aqueous environment. Thus, the ultrasonic-assistant fore-modified method was potential in dramatically improving the feature of biochars. SFB presented excellent adsorbability to antibiotics and exhibits extraordinary potential in wastewater treatment.