In order to find out the principle of wool keratin dissolved in molten urea,SDS-PAGE method was used to determine the molecular weight of dissolved wool keratin firstly.Secondly,standard compounds such as vanillin,vanillyl alcohol,vanillic acid,acetyl vanillin,formyl vanillic acid,4-acetyl-3-formyl succinic acid,salicylanilide,3,3-dihydroxydiphenyl disulfide,aniline,tyramine acid were used to substitute the functional group and chemical bond in wool keratin,respectively,and react with urea at 150℃ for 20 min,separated 3 times with ethyl acetate,dehydrated and concentrated for the organic layer,dissolved with acetone,and analyzed by GC-MS.Aqueous layer was freeze-dried,ethylationed,concentrated for GC-MS analysis.The result showed that,the wool keratin with high molecular weight,75 ku,still maintained a high molecular state.The aldehyde group was detached,the ester bond was only deacetylated,the carboxyl group was detached or bound to urea,the alcoholic hydroxyl group and the amino group were combined with urea,and the peptide bond and the disulfide bond were not broken.Main approaches of the dissolution mechanism of wool in molten urea were hydrogen bond cleavage,functional group detachment,urea bonding to functional group,etc. The primary structure of wool keratin was not destroyed and still maintained a high molecular state.The amino and carboxyl groups of tyrosine reacted with urea to form a cyclized structure,which could be dissolved in an organic solvent and could be detected from the analysis of GC-MS.There were neither compounds that were converted from raw materials,nor the raw materials themselves in the aqueous layer of all standard compounds and urea reaction products,so improvement of experimental method was needed for further research.