ObjectiveTo understand the inpatient classification and influence factors of hospitalization expenses, so as to provide basis for hospital management. MethodsThe diagnosis and treatment data of inpatients in a grade A tertiary hospital in 2013 were collected, the percentile method were used to describe the expenses distribution, the K-means clustering method was applied to classify the inpatients, the rank-sum test was utilized to analyze the differences of the costs among different groups, ICD-10 was applied to analyze the diseases distribution, and the median regression was used to analyze the influence factors. ResultsThere were 175 333 inpatients in total. The median of the expenses was 10 016.31 yuan RMB. The inpatients might be classified into seven groups with different expenses (P=0.0001). For inpatients who had no "blood transfusion cost", the top three factors of cost category were operation, laboratory test, examination; for who had "blood transfusion cost", the top three factors of cost category were blood transfusion, laboratory test, examination. There were 2 147, 2 182, 1 499, 1 301, 2 059, 22 and 14 kinds of diseases (ICD-10 four-digit code) respectively among the seven groups. The influence factors could be summarized into patient-related and diagnosis & treatment-related ones. ConclusionThe costs of operation, blood transfusion, laboratory test, and examination affect the inpatients classification greatly. The results could be of help to inform the admission of patients, the expense control and the disease management.