With the development of flexible and straightening technology, transient protection has ushered in an upsurge of research at home and abroad, and the current research progress of protection action speed has approached its limit. The improvement of protection recognition speed will inevitably be accompanied by a decrease of reliability. So how to improve the reliability of protection under the requirement of ensuring quick motion is the most important thing. Lightning strikes occur frequently in long-distance power transmission projects, and they cannot be ignored as a source of interference without causing flashover. For this reason, this paper uses the Hilbert Huang transform to design a high-frequency protection scheme. At the same time, it uses the characteristics of the lightning wave to propose a lightning interference identification method. Then the lightning strike and protection criteria are combined to make up for the shortcomings of transient protection and improve its reliability. Finally, the Zhangbei four-terminal flexible DC system and the lightning current model are built in the PSCAD simulation platform to complete the verification of the protection method. It has been verified that the protection method designed in this paper can accurately identify fault poles and internal and external faults, and will not malfunction because of lightning interference. At the same time, the protection has a high resistance to transition resistance. This work is supported by the Science and Technology Project of the Headquarters of State Grid Corporation of China (No. KJ21-1-66).