In order to better test the fault treatment performance of the distribution automation system， a host injection testing method is put forward that is capable of simulating various faults on the feeders to test the feeder-automation behavior of a distribution automation system. The composition of the proposed host injection testing platform is described. The principle and basic steps of the host injection testing platform are detailed. The application results show that the proposed method is suitable for use as a test tool in factory acceptance test， site acceptance test and practical testing.