This paper presents an earth fault location algorithm based on optimization approach., which is developed for MV distribution networks with resistance-earthed neutral. The objective function is written based on relation between voltage and current measurements at substation, line parameters, fault distance and fault resistance. The optimization process is performed with MATLAB Optimization Toolbox that gives values to the last two variables. To deal with the heterogeneity of MV feeders, fault location is carried out successively on every homogeneous section lines and the optimal points of the different sections will be compared to give the final solution. The performance tests, which are performed on a MV CIGRE benchmark network, show encouraging results. In this study, impacts of load consumption uncertainty and of DG connection are also discussed.