Abstract: An isocyanate trimer modified with silane or functional polysiloxane and having formula of wherein R represents tolyl, ethylphenyl, diphenylmethyl, 1,5-naphthyl, hexamethylene, isophorone, 2,2,6-trimethylcyclohexyl, or 4,4-dicyclohexylmethyl, etc.; R1 is saturated or unsaturated and linear or branched C1-8 alkyl, cycloalkyl, aryl etc., or a homologue of aromatic hydrocarbon; R2 and R3 at each occurrence separately represents C1-6 alkyl, aryl, trialkylsilyl, methoxyalkoxyl; a is an integer from 0 to 3; R1, R2, R3, R4, and R5 at each occurrence separately represents saturated or unsaturated and linear or branched C1-12 alkyl, cycloalkyl, alkoxyl, or aryl etc.; X represents —NH—, —NHCH2CH2NH—, —NHCH2CH2NHCH2CH2NH—, —N—, —NHCONH—, —S—, or —O—, and n is an integer which is ?0. A method of preparing the compound is also provided.