In order to assess the capacity of approach area in Xia’men GAOqi aerodrome, which had set up Performance Based on Navigation (PBN) flight procedure, this article used the Monte-Carlo method, analyzed the procedure, collected the flight data in accordance with the traits of PBN flight procedure, and built the Monte-Carlo calculating model whose origin was Intermediate Fix (IF). This article also tested the feasibility of using the model to assess the capacity in approach area based on PBN flight procedure.