The purpose of this paper is to review the empirical study results of conversion factors(unit prices) for relative values of health care services in the national health insurance system and establish optimal classification of health care institutions for feasible contract of conversion factors between National Health Insurance Corporation(NHIC) and provider groups, based on legal backgrounds and types of health care service delivery system. some empirical research evidences shows the validity of applying multiple conversion factors to annual contract for reimbursement in the national health insurance. Policy recommendations suggest that clinic, hospital, general hospital, tertiary hospital, dental clinic, oriental medical clinic, pharmacy, and public health centers would be a basic category of provider groups for a meaningful price contract between the NHIC and providers.