This paper reports the clinical characteristics, diagnosis, and treatment of the first critical COVID-19 patient in Liaocheng City, who was admitted to the intensive care unit isolation ward of Liaocheng People's Hospital on February 11, 2020. On admission, the patient had difficulty breathing, the oxygenation index was 135 mmHg, and the blood lactate was 5.6 mmol/L. After comprehensive treatment including high-flow nasal cannula oxygen therapy, plasma exchange, antiviral and anti-infection therapies, immune regulation, liquid volume management, glucocorticoid, enteral nutrition support, analgesia and sedation, blood glucose control, anticoagulation and thrombus prevention, and electrolyte balance maintenance, the patient was finally cured, and discharged. The purpose of this case report is to provide a reference for the clinical diagnosis and treatment of critical COVID-19 patients.