In order to better analyze the stable sub-safety state and unstable sub-safety state existing in control sector operation，K-means algorithm was used to cluster three control sector operation stability evaluation indicators of excess-capacity ratio(ECR)，retention degree and flight attitude mixing ratio so that the optimal classification of the operation stability of control sector was determined. The index threshold corresponding to each level was obtained by clustering analysis of a single index. Combined with the index weight calculated by the entropy weight method，the operational stability level of the control sector in each time period was obtained according to the principle of maximum membership degree. Then，the comprehensive evaluation model of control sector operation stability was constructed. The actual flight data of Xiamen No.01 sector was selected to more comprehensively analyze operation situation of control sector from the perspectives of stability and trend. The results show that the best effect is obtained when the control sector operation stability level is divided into three categories. The stability varies with time due to the influences of air traffic flow and control conditions，especially in the two time periods of 7: 30-9: 15 and 20: 00-21: 00，when the change of stability is most obvious. The controllers need to pay great attention to improving the safety of airspace operations.