Abstract: The catapult's quantity deployed is a major influencing factor on carrier aircrafts' sortie generation rate.In the incipient designing period, the catapult quantity is also one of the important factors.Considering the queuing characteristic of the launch process as well as the closed characteristic of the launch and recovery process, this paper proposes a closed queuing network based model for evaluating the influence of the catapult's quantity on sortie generation rate, which can be applied to the design of catapult's quantity. For validation, an example is designed based on the F/A-18's sortie and the recovery process in the Surge operation, whose calculating results agree well with the Surge operation.