Surface charge properties of an adsorbent always play an important role for the removal of contaminants from water. A cationic surfactant hexadecyl tri-methyl ammonium bromide (CTAB) was involved into adsorptive removal of Orange II (ORII) by bagasse biochars to realize an in-situ modification and an enhanced adsorption capability. Adsorption capacity of biochar (BC600) improved significantly from 1.66mg/g in the absence of CTAB to 4.42mg/g in the presence of 2.0mg/L CTAB. A more hydrophobic surface of bagasse biochar was favorable for the dye uptake in the presence of CTAB. Linear pseudo-second-order kinetic model fitted the kinetics data better at three pH conditions than pseudo-first-order kinetic model, whether in the presence and absence of CTAB. Both nonlinear pseudo-first-order and pseudo-second-order kinetic models were suitable to describe the experimental data. The maximal adsorption capacity in the absence of CTAB was very limited (41.4mg/g), while the adsorption isotherm curve in the presence of CTAB was almost linear, indicating a strong adsorption capability due to the introduction of CTAB. Direct addition of CTAB into wastewater is a potential technique for the enhanced removal of negatively-charged pollutants by bagasse biochar.