Abstract: This case reports an elderly male patient who was diagnosed with COVID-19 (critical type),and was treated with Paxlovid, dexamethasone,baricitinib, anticoagulant, Prone ventilation and oxygen therapy. When COVID-19 nucleic acid turns negative and specific antibodies are produced, high fever and inflammatory indicators rebound, complicated with involvement of multiple systems (cardiovascular system, kidney, nervous system), was diagnosed as multisystem inflammatory syndrome in adult(MIS-A).After glucocorticoid therapy, the patient's symptoms were relieved and the prognosis was good.

Key words: COVID-19, multisystem inflammatory syndrome in adult, glucocorticoid, anticoagulant therapy