The traditional method of identifying non-fault line tripping is based on full current. When the amplitude of running current before fault and the amplitude of reactive current after fault is close to being equal, the traditional method of identifying non-fault tripping cannot reliably recognize it. In this paper, a new method of non-fault UHV AC line trip criterion in security and stability control system is proposed, which identifies the non-fault tripping based on active current. It can filter the reactive components of the line’s current after the line trip. The new method is upgraded on the basis of the traditional criteria logic. When the non-fault tripping aforementioned occurs, the new method can recognize it reliably. The theoretical analysis and dynamic simulation validate the reliability of the new method. This work is supported by Science and Technology Project of State Grid Corporation of China (No. SGTYHT/ 17-JS-199) “Standard Research on Primary Substation Equipment of Safety and Stability Control System”.