Polycrystalline ceramic Nd0.7Sr0.3MnO3 is synthesized using high-energy ball milling and post heat treatment method. The properties of electric transport are measured using direct current (DC) 4-wire and 2-wire methods. The results show that both the grain (phase) boundary and the electrode-bulk contact interface has interfacial resistance and space charge layer. The two kinds of space charge regions have greatly different effects on the DC transport: for the former, the I-V curve exhibits nonlinear characteristic and no EPIR effect takes place; for the later, however, an obvious EPIR effect is observed even if the I-V curve also shows nonlinear behaviour. It well suggests that for the ceramic Nd0.7Sr0.3MnO3, only the electrode-bulk contact interface can induce the EPIR effect although there is a similar nonlinear I-V characteristic for the grain (phase) boundary and the electrode-bulk contact interface.