The shortage of energy and the deterioration of the environment have become increasingly prominent. A large number of distributed generation access to distribution network, network structure changes. Because of the fast response characteristic of the inverter interfaced distribution generation (IIDG), the instantaneous current protection of distribution network appears to be wrong or refused to move. In this paper, based on the research on the limit current of IIDG, the longitudinal protection scheme based on the amplitude comparison method is studied. In order to adapting to the fault of the transition resistance, protection scheme joins the negative sequence of the discriminant, Constituting a comprehensive range of discriminant protection scheme. In the PSCAD simulation of different fault types, different transition resistances and limit distribution network distance protection action, the protection can be the correct action, indicating the protection of adaptability.