Modified chitosan was prepared with chitosan, ethyl acetate, and epichlorohydrin at ratio of 30:1:1(v/v). This prepared material was evaluated by FT-IR spectra, SEM images, and UV spectra analysis. FT-IR spectra results indicated that epichlorohydrine might have reacted with chitosan and the modified chitosan had been formed. SEM image analysis showed that the addition of epichlorohydrine had important effect on the crystallinity. The adsorption test indicated that the modified chitosan exhibited a faster kinetics for the adsorption and desorption of olaquindox in 3 hours; modified chitosan offered higher selectivity and adsorption capacity toward olaquindox than that of structurally related compounds.