Nowadays, a large number of distributed power sources and unmeasurable load branches are connected to the distribution network, and the original protection scheme cannot meet the requirements of the new distribution network. By analyzing the asymmetric fault characteristics of active distribution network with unmeasurable load branches, a negative sequence fault superimposed network equivalent model inside and outside the area is established. By analyzing this equivalent model, the different model expressions of the protected lines under internal and external fault are extracted to design protection criteria based on model identification. A protection scheme based on the negative sequence fault superimposed network model identification is designed. A 10 kV active distribution network model identification is built by using PSCAD simulation software to validate the proposed scheme. The results show that the scheme can accurately identify the fault area.