The principal purpose of this paper was studied the life-cycle cost analysis (LCCA) of existing prestressed concrete (PC) bridges. A reasonal analytical model was established and provided for evaluating existing PC bridges. This model consists of design, production, quality assurance, capital benefit and other costs. To verify this analytical model, two existing PC bridges in Taiwan were used as illustrative examples. The results of present study show that the analytical model is very reasonable, reliable, and serviceable. The results represented in this study may be used as an engineering decision-making tool for the repair, strengthening or demolition rankings for existing PC bridges.