COVID-19 infection can progress to severe pneumonia, pulmonary edema, acute respiratory distress syndrome, or multi-organ failure. A severe inflammatory response contributes to the clinical manifestations of patients with COVID-19. Therefore, circulating biomarkers such as C-Reactive Protein (CRP) Value, Total Lymphocyte Count (Tlc) can represent inflammation which can be a good predictor for the prognosis of COVID-19 patients. This study aims to determine the Relationship Between C-Reactive Protein (Crp) Value, Total Lymphocyte Count (Tlc), Lung Compliance And P/F Ratio In Critical Covid-19 Patients With Mechanical Ventilators In ICU. This research is a descriptive observational study with a cross sectional design (cross-sectional). The method used in this study is diagnostic analysis by assessing sensitivity, specificity, positive predictive value and negative predictive value. Data retrieval was carried out retrospectively which was taken from tracing data documents of COVID-19 patients who were treated in the ICU of RSUP Dr. Hasan Sadikin. Low levels of lung compliance are known to predict the length of stay in the ICU but cannot predict the mortality rate of critically ill COVID19 patients. There is a significant relationship between the value of C-Reactive Protein (CRP), Total Lymphocyte Count (TLC), Lung Compliance and P/F Ratio with the prognosis of critically ill Covid-19 patients in the ICU Dr. Hasan Sadikin.