In order to quantitatively analyze air traffic operation complexity,multidimensional metrics were selected based on the operational characteristics of traffic flow.The kernel principal component analysis method was utilized to reduce the dimensionality of metrics,therefore to extract crucial information in the metrics.The hierarchical clustering method was used to analyze the complexity of different airspace.Fourteen sectors of Guangzhou Area Control Center were taken as samples.The operation complexity of traffic situation in each sector was calculated based on real flight radar data.Clustering analysis verified the feasibility and rationality of the method,and provided a reference for airspace operation and management. In order to quantitatively analyze air traffic operation complexity, multidimensional metrics were selected based on the operational characteristics of traffic flow. The kernel principal component analysis method was utilized to reduce the dimensionality of metrics, therefore to extract crucial information in the metrics. Hierarchical clustering method was used to analyze the complexity of different airspace. Fourteen sectors of Guangzhou Area Control Center were taken as samples. The operation complexity of traffic situation in each sector was calculated based on real flight radar data. Clustering analysis verified the feasibility and rationality of the method, and provide a reference for airspace operation and management.