The invention discloses a method of recognizing a power system transient stability negative correlation section based on a trajectory, which belongs to the field of power systems and automatic technology thereof. The method of the invention is based on a power system transient stability quantification theory, system units are divided into a preceding group and a remaining group, a two-unit system is further formed equivalently until a single unit infinite system is formed equivalently, the number of peaks in first swinging of a system equivalent single unit infinite system power-angle response curve is used for initially judging whether a transient stability negative correlation section possibly exists in the system, if the peak number is larger than 1, two-unit equivalence based on an inertia center is further carried out on the preceding group and the remaining group respectively, and through comparing a power-angle phase difference at any moment of equivalent two units in different groups, whether a transient stability negative correlation section exists in the system is finally judged. A power system dispatching operator can master the internal operation rules of the grid, a grid dispatching operation control decision is made, and safety, stability and the automatic level of the system are enhanced.