Before handing over command of arrival flights to terminal controller, en route air traffic controller should adjust arrival flight queue as an appropriate sequence since air traffic flows aggregate at the entrance of air-corridor near airports. A good adjustment needs to consider such target as ensuring safe separation of adjacent flights by issuing adjustment commands as less as possible. This paper introduces a concept of approach adjustment and presents the mathematical description of the problem of approach sequence adjustment, which integrates both human experience and precise computing model. An intelligent sequence-adjusting algorithm is also discussed, which is based on general satisfaction function consisting of three factors: safety, capacity and equilibrium. Tested on practical data, the algorithm has good effectiveness.