Abstract: The invention “use of biomarker or biomarkers combination in preparing a diagnostic reagent for fulminant myocarditis and a drug for fulminant myocarditis” belongs to the field of disease diagnostic reagents and drugs. The biomarker comprises Siglec-5. The biomarkers combination is further selected from the group consisting of sST2, PAI-1, Siglec-5, CD163, CD40, P-Cadherin, CD14, CTLA4. The invention finds that the levels of the biomarker in plasma of patients with fulminant myocarditis is increased, and proves that the biomarker plays a role in diagnosing fulminant myocarditis and a role as a drug target in relieving and/or improving fulminant myocarditis. The level of the biomarker can be detected to forecast or auxiliary diagnose fulminant myocarditis or estimate prognosis of fulminant myocarditis. Meanwhile, level of the biomarkers is controlled through drugs, more intensified diagnosis and follow-up treatment can be carried out on diseases, and the biomarkers have huge clinical application value.