Using low-cost agro-industrial wastes and by-products derived from lignocellulosic biomass for adsorption is believed to an affordable and sustainable way to tackle the burning issue of cationic pollution in the marine, while its relatively low adsorption capability limits its large-scale application. Chemical modifications to improve the adsorption abilities of lignocellulosic biomass usually has problems such as long reaction time, high operational cost, rigorous reaction conditions (high temperature and pressure) as well as the second pollution. In this study, a green, rapid, simple, and mild method was developed by using ozone to improve the adsorption abilities of sugarcane bagasse (SB). The effects of ozone modification on the SB and its related adsorption abilities towards cationic polymers were quantitatively investigated. Results showed that ozone modification under very low ozone consumption (~ 1.5 wt%) could efficiently increase the carboxyl groups, change the chemical compositions of SB, and does not significantly change its morphology, thereby ensuring the good recovery and adsorption performance of SB. The maximum adsorption rate and capacity of SB for positively charged methylene blue (MB) were increased about 33.3% and 11.3% than the original SB. Besides, ozone modified SB maintained its high adsorption capability even at high NaCl concentration (0.6 M). For cationic polymer with high charge densities, the adsorption capacity of milled SB increased about 125.4%.