Based on the data of daily wind direction and surface temperature over the China Southern Coast and the wind velocity over the northern South China Sea (NSCS),the northerly cold surge criterion and the occurrence frequency of the cold surge over NSCS were defined.In addition,the interannual variation of the cold surge over NSCS and the variation of its associated circulation have been investigated.The results show that the occurrence frequency index of the cold surge over NSCS can describe the cold surge system characteristics more comprehensively.It is closely associated with the outbreaks of cold air which influence most part of China,and results from the interaction between the middle and high latitude circulation and lower latitude circulation.When the ridge over the west of the Lake Baikal is stronger than normal,the meridionality of the circulation over middle and high latitudes becomes larger,at the same time the subtropical western Pacific high becomes weaker and is located further east than normal.Both of these are beneficial for the southward movement of the cold air,and lead to the cold surge's formation over the NSCS.When the cold surge occurs,the Hadley cell becomes stronger and it adjusts the air quality over the middle and high latitudes.Meanwhile,the subtropical westerly jet resulting from the high-level air northward movement under the action of the Coriolis force becomes stronger than normal.Both of these elements are beneficial for the maintenance and strengthening of the cold surge.