Health insurance in Vietnam has been used as part ofthe efforts to bring more resources into the health sector.As far as voluntary health insurance schemes in Vietnam isconcerned, the Voluntary Health Insurance Scheme in Haiphongis a typical example of most voluntary health insuranceschemes in Vietnam where the gap between target number ofinsured person and the actual number of people reallyinsured remains a long standing problem. This study aim tohelpsolve this problem by conducting a case study oneconomic analysis of voluntary health insurance premium inHaiphong. The study attempted to identify the method toestimate the optimal premium for VHI scheme, which expectedto be used as one of the means to extend the membership ofthis program, not only in Haiphong, but also in otherlocations as well. This study is an analytical study based on bothsecondary data and surveyed data. In the initial stage, thecriteria of optimal premium was established then optimalinsurance premium was estimated using logit model based oncertain price elasticity of demand with the assumption thatsupply of health care services is constant in the short run.After that, data collected from small pilot survey inHaiphong are use to hypothetically demonstrate the researchmethodology. Final result of this study showed the optimalpremium of Voluntary Health Insurance scheme in Haiphong is12,672 dong, A further study will be needed to establish themethodology to estimate optimal premium for compulsoryhealth insurance scheme and where supply side in the shortrun is not perfectly elastic.