On June 16 and July 13, 2019, two major power outages occurred in Argentina and Manhattan, New York. This paper introduces the operation status of the power grid before the accident, the cause, process and recovery of the accident, and points out that the main causes of the accident are the lack of necessary stability analysis, the defects of the safety control, the wrong operation of the protection and the unreasonable configuration of the "third line of defense". In combination with the actual situation of China’s power grid, some suggestions are put forward, such as attaching importance to the protection, setting and operation maintenance of safety and control devices, to ensure the safe and stable operation of power grid and prevent the occurrence of major power failure.