For the security access problem of the massive edge devices in the power Internet of Things, the secure access authentication technology for edge devices in power Internet of Things was researched, which set such mechanisms as protocol filtering, protocol adaptation, network isolation, access authentication in an organic whole. Based on above technology, a secure access authentication device applied to the power Internet of Things was designed, which included external network processing unit, isolation exchange unit, system management unit, cipher operation unit and internal network processing unit. Then the pilot application and performance test analysis for the devices was carried out. The test results show that the secure access authentication device can realize the secure access authentication for massive devices in the power Internet of Things under the premise of basically not affecting the communication performance of the devices. It still has good reliability and generalization when facing the access of different types of edge devices, and can effectively reduce the risk of the core business system being illegally invaded.