NOVELTY - Organically modified activated carbon material (A) is claimed. (A) is obtained by activating activated carbon with substituted siloxane compound (I) to obtain graft initiator activated carbon, and then carrying out polymerization of graft initiator activated carbon with substituted olefinic monomer (II) to obtain final product, where activated carbon is raw material of nitric acid, hypochlorous acid, sulfuric acid or hydrogen peroxide.    USE - The organically modified activated carbon material is useful in adsorption of methane composite material (claimed).    ADVANTAGE - The organically modified activated carbon material reduce the pore size of activated carbon large pores and has good adsorption performance.    DETAILED DESCRIPTION - Organically modified activated carbon material (A) is claimed. (A) is obtained by activating activated carbon with substituted siloxane compound of formula (I) to obtain graft initiator activated carbon, and then carrying out polymerization of graft initiator activated carbon with substituted olefinic monomer of formula (II) to obtain final product, where activated carbon is raw material of nitric acid, hypochlorous acid, sulfuric acid or hydrogen peroxide.    X1, X2 = F, Cl, Br or I;    R1-R4 = 1-3C alkyl group;    n = 3-6;    R5 = H, 1-3C alkyl group;    R6 = COOR7 or aryl; and    R7 = 1-6C n-alkyl.    INDEPENDENT CLAIMS are also included for:    (1) preparation of (A) comprising (i) carrying out nitric acid treatment of activated carbon to obtain modified activated carbon, mixing activated carbon material with an aqueous solution of nitric acid in a weight ratio of 10-20:1-5, reacting at 0-60 degrees C for 1-10 hours, filtering, washing and drying to obtain modified activated carbon, where mass fraction of nitric acid in aqueous solution of nitric acid is 10-90%, (ii) adding nitrified activated carbon, (I) and basic substance in a molar ratio of 1-60:1:1-10 to an organic solvent, and reacting at 0-100 degrees C for 1-24 hours to obtain graft initiator activated carbon, and (iii) carrying out polymerization of graft initiator activated carbon and (II) in molar ratio of 1:100-350 in presence of catalyst at 0-100 degrees C for 1-24 hours, centrifuging, washing, and drying to obtain organically modified activated carbon material, where catalyst is copper bromide/ N,N,N',N'',N''-pentamethyldiethylenetriamine, copper bromide/2,2'-bipyridine, copper bromide/tris(2-(dimethylamino)ethyl)amine, copper chloride/N,N,N',N'',N''-pentamethyldiethylenetriamine, copper chloride/2,2'-bipyridine and/or copper chloride/tris(2-(dimethylamino)ethyl)amine; and    (2) use of (I) in adsorption of methane composite material comprising 50-99% organically modified activated carbon material.