Abstract: With the increase of voltage level and transmission capacity, flexible DC systems have put forward higher requirements for line protection. Especially for long-distance, large-capacity flexible DC systems, the protection of the line plays a key role in the stability of the entire system. Lightning strikes and other disturbances have a great influence on the protection of the line. Based on the analysis of the characteristics of both sides' line mode current's forward wave under the conditions of normal and lightning strikes in the VSC-HVDC transmission system, it is found that the difference between both sides' line mode current's forward wave has some relationship.According to this feature, this paper proposes a new energy ratio-type non-fault lightning strike and fault lightning strike and short-circuit fault identification criteria. The method effectively solves the influence of the high-frequency interference source generated when the line is struck by lightning on the protection. The principle is simple, the calculation is simple, and it has a high speed of action. Simulations with pscad demonstrate the reliability of the method.