The invention relates to a protein marker for sicca syndrome in saliva and application of the protein marker. Particularly, the invention relates to application of a protein identification reagent inpreparation of a reagent for diagnosing the sicca syndrome in a subject. Protin is selected from a combination of acylamino acid release enzyme, 1,4-glucose formyl transfer enzyme, Calumenin, C-C motif chemotatic factor ligand 28, activation-induced cytidine deaminase, alpha collagen 1 chain, carboxypeptidase D, carboxypeptidase E, cysteine proteinase inhibitor C, cathepsin L, DnaJ heat shock protein family (Hsp40) member C3, furan paired basic amino acid lyase, HtrA serine peptidase 1, kallikrein correlated peptidase 11, trypsin 3, proteasome subunit-4, proteasome subunit 9, antichymotrypsinand vimentin.