Biochar, a carbon material, has become an attractive material for various applications due to its intriguing properties. The characteristics and adsorption performance of biochar depended on synthesis conditions. Hence, this work aimed to study the influence of activating agents and pyrolysis temperature on the structure and adsorption performance of biochar. The activated biochar (AB) was prepared by treatment of raw water hyacinth (an agricultural waste) with different activating agents including ZnNO3, FeCl3, NiCl2, KOH and HNO3 before treatment at high temperature under N2 atmosphere. The obtained AB samples were characterized by XRD, SEM, Raman, and BET. The activating agents strongly affected on the structure of the AB and methylene blue adsorption performance. The ZnNO3-activated biochar exhibited highest MB removal, compared to the KOH-, FeCl3-, NiCl2-, and HNO3-activated biochar. In addition, it was found that the pyrolysis temperature significantly enhanced the adsorption performance. The MB removal increased from 21.4 % to 99.4 % corresponding to the increasing of the temperature from 500 to 800 °C. Moreover, the highest MB adsorption capacity was 59.6 mg g-1 for Zn-BC-800.