Bagasse xylan gallate was synthesized by using bagasse xylan as main raw materials, gallic acid as esterifying agent, triethylamine as activation catalyst and N, N-dimethyl formamide (DMF) as the solvent. The esterification and graft copolymerization of methacrylic acid (MAA)/ butyl acrylate (BA) grafted onto bagasse xylan gallate was carried out by using ammonium persulfate as initiator. The parameters of the process affected on the degree of substitution (DS), grafting rate (G) and grafting efficiency (GE) were investigated. The structure and properties of the product were characterized by FTIR, SEM, XRD and TG-DTG. The results showed that the DS was 0.64 under the conditions of n(bagasse xylan): n(trisacetyl-galloylchloride)=1: 1, m(DMF): m(bagasse xylan)=9.5: 1, the esterification reaction temperature 45 ℃ for 4 h. The grafting rate and grafting efficiency of the product was 23% and 67% under n(bagasse xylan gallate): n(BA/MAA)=1: 2, with the ammonium persulfate dosage being 7% (the total reactant mass), reaction temperature 50℃ for 8 h. The product of anti-cancer activity was evaluated against some tumor cell lines by using a methylthiazolyldiphenyl-tetrazolium bromide (MTT) method. The results showed that the inhibition rate on cancer cells of the liver reached to 28.83%.