Abstract: On January 8, 2021, the synchronous power grid in the continental European area was divided into two regions: the northwest part and the southeast part. There were 1700MW interruptible loads having been cut off in France and Italy. About 70MW loads in the northwest area and about 233MW loads in the southeast area were cut off due to the extreme voltage and frequency variations. This paper introduces the general situation of the European power system, sorts out the development process of the accident, and summarizes the causes of this accident. Combining with the actual situation of China's power grid, it puts forward the enlightenment of this disconnection accident on the development of China's power system.