In this study, an energy loss analysis technique for campus distribution systems is proposed. For energy losses evaluations, the mathematical models of system components are established and verified. To examine the factors affecting energy losses of a distribution system, the full-scale digital models of distribution systems are developed as a platform. Furthermore, the continuous three-phase power flow is used to evaluate the whole system energy losses. In this study, the distribution systems in Yuan Ze University (YZU) are adopted as benchmarks for evaluating and solving energy loss problems.