Abstract: It is particularly important to study the safety margin of the continuous descent final approach (CDFA) as it has been widely used in China.This study analyzes the safety margin of the key steps in the process of CDFA,and a safety evaluation model is developed.On the basis of the literature reviews,the safety marge of CDFA is analyzed for the following:normal conditions,abnormal conditions and exchange of aircrew.This study proposes an index system model based on the relationship between the workload of the aircrew and safety margin.The parameters of the cloud model are calculated according to the related algorithm of the cloud model,and a distribution map of the cloud model was developed using Matlab.The results show that the interval values of the cloud model for the aircrew exchange range from 4.76~8. 99 during the CDFA process,which is significantly higher than those under the normal conditions and abnormal condi-tions.Therefore,the workload of the pilots who implements CDFA process will significantly increase when the problems arise during the aircrew exchange process.