Electronic medical record (EMR) systems have been proposed as technology to improve the quality of patient care, decrease medical errors, control and reduce medical expenditure, however the financial effects have not yet been as well documented in China. We presented a net financial cost-benefit analysis of implementing electronic medical record systems in general hospital in China. The data, which were obtained from studies of the general hospital and the published literature, collected from 15 consecutive fiscal months from May 1, 2009 to August 30, 2010. We performed a perspective cost-benefit study to analyze the financial effects of EMR system implementing. The reference strategy for comparisons was the traditional paper-based medical record. The net financial benefits or costs for a 6-year period were calculated. All data were adjusted for inflation. The totally assessed net benefit from implementing an EMR system for a 6-year period was $559,025 in the general hospital. Benefits accrue primarily from savings in new medical record creation, decreased full-time-equivalent (FTE) employees, saving of adverse drug events (ADEs) and dose errors, improved charge capture and decreased billing errors. In this model, the time of return on investment is 3.00 years. In one-way sensitivity analysis, the model was most sensitive in new medical record creation; the net benefit varied from $398,057 to $719,992. The five-way sensitivity analysis with the most pessimistic and optimistic assumptions showed results ranging from a $76,970 net cost to a $1,062,122 net benefit; the pessimistic time of return on investment is 5.38 years. An EMR system cost-benefit analysis can rapidly demonstrate a positive return on investment when implemented in hospitals. The magnitude of the return is sensitive to several key factors.