Objective To analyze the characteristics of nonagenarian inpatients in internal medicine department and investigate the influencing factors associated with the in-hospital mortality. Methods Medical records of 141 over-90-year-old inpatients admitted in our department from January to December 2014 were collected and then retrospectively analyzed. According to their in-hospital outcome, the patients were divided into death group (n=29) and survival group (n=112). The general information, results of bio-chemical indices at admission, Barthel index (BI) activities of daily living (ADL) were compared between the 2 groups for influencing factors associated with the in-hospital mortality. SPSS statistics 16.0 was used to analyze the data. Student′s t test, Wilcoxon rank sum test or Chi-square test was employed for the comparison between groups. Multivariate logistic regression analysis was adopted to explore the factors affecting in-hospital mortality. Results Compared with the patients in the survival group, those from the death group had higher ratios of acute or old myocardial infarction, atrial fibrillation, anemia, hypoalbuminemia and cancer (P<0.05), lower BI [(37.93±25.27) vs (61.92±23.64)], and decreased levels of hemoglobin [(110.11±20.79) vs (120.59±16.83)g/L] and albumin [(35.42±4.67) vs (38.35±4.25)g/L], but larger white blood cell count [(8.89±4.75)×10⁹/L vs (6.95±2.26)×10⁹/L]and higher level of high sensitivity C-reactive protein [19.44(6.99,0.77) vs 5.18(1.27,3.48)mg/L] (all P<0.05). Logistic regression analysis indicated that severe and very severe disability(OR=5.055,5%CI 1.961-13.026,P=0.001), anemia (OR=4.796, 95%CI 1.795-12.813,P=0.002), and white blood cell count (OR=1.233,5%CI 1.046-1.455,P=0.013) were risk factors for in-hospital death in the cohort. Conclusion The inpatients aged 90 or above should actively improve their ability of daily living after admission, and the state of anemia should be corrected initiatively.