Background: Currently there is variability in diagnostic procedures across countries. Our aim was to compare guidelines of brain death determination in adults among five countries: China, UK, US, France, and Germany.Method: This is a retrospective study based on a prospective database of consecutive coma patients who received brain death determination. The technical specifications, completion rates, and positive rates of brain death determination according to criteria of different countries were compared. The accuracy, sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of each ancillary test for the identification of brain death diagnosed according to different criteria were investigated.Results: One hundred and ninety-nine patients who received brain death determination from June 2018 to June 2020 were included in this study. One hundred and thirty-one (65.8%) patients were diagnosed with brain death according to French criteria, 132 (66.3%) according to Chinese criteria, and 135 (67.7%) according to criteria of US, UK, and Germany. The sensitivity and PPV of EEG (92.2% - 92.3%) and SLSEP (95.5% - 98.5%) were higher than TCD (84.3% - 86.0%), and all these three tests have a very low specificity and NPV.Conclusions: The duration of apnea test and requirements of ancillary tests vary among countries. The discrepancy in brain death determination between clinical assessments and additional confirmation of ancillary tests is small.