To reduce the cost of airline fleet during flying and improve aircraft load factors, optimization matching between fleet models and routes is researched. The effect of passenger overflow on the airline cost is analyzed. Considering the flight covering, passenger demand, fleet life and flight continuity, a 0-1 integer programming mathematical model is established. Furthermore, the model is solved by using multi-objective fuzzy decision making based on membership degree. Comparison results of the simulation data with the original plan data prove that the mathematical model of multi-objective optimal allocation of fleet has realistic significance of reducing the flight cost and improving the seat utilization.