Objectives: To investigate the affecting factors on expenditure in Medical insurant inpatients. Methods: 593 medical insurant inpatients, who were from Feb 1, 2001 to Feb 31, 2002 in Nanjing Jinling hospital, were enrolled in this study. The inpatient expenditure was analyzed from the aspect of operation or not, age, and payment mode, used the descriptive analysis and multi factor analysis on affecting factors of the total expense, self bearing expense, and self affording expense. Results: The hospitalized days, operation or not, severity of disease were important affecting factors. The self bearing expense of medical insurant inpatients was associated with hospitalized days, operation or not, and total expense. While the self affording expense of them was associated with expense of drug, hospital bunk, radiation and others. Conclusions: We can control these associated affected factors to lighten the economic weight of patients, and to reduce the ratio of individual payment.