Objectives: This study aims to investigate the changes in medical utilization of those who sought medical care services only in hospital sector after the implementation of Hospital Global budget payment System; thus, the implications for improving healthcare resources allocation can be derived. Methods: The study included 4043 subjects who sought medical care only in hospital sector during the period of two years prior to the implementation of Hospital Global Budget Payment System in July 2002. The data of their utilizing ambulatory and inpatient services in the period of July 2000 to June 2004 which are divided into eight sub-periods of half a year are analyzed. Results: Two major findings are as following: (1) The utilization of inpatient services in per half a year sub-periods after the implementation of Hospital Global Budget Payment System has increased by 5.6-18.2%, while the number of ambulatory visits and the claimed points of outpatient services in hospital sector decreased by 1.0 and 0.4%, respectively. (2) Though the number of ambulatory visits in hospital sector has decreased by 0.05-0.69 visits, the total visits including both clinics and hospitals still increased by 0.05-1.09 visits. Conclusions: Though ambulatory utilization of the patients has decreased in hospital sector after the implementation of Hospital Global Budget Payment System, the total outpatient visits including clinics and hospitals still increased. It seems to show that the patients shifted from hospitals to clinics. However, it needs further investigation to see if the transferred patients were in less severe conditions. Moreover, the relevance of separating the hospital and clinic global budgets deserves review.