The airside performance of a fin-and-tube heat exchanger with flat slotted fin shape is investigated by using a commercial code FLUENT based on the finite volume method implementing SIMPLE algorithm, and a variety of improved fin models are proposed. Three-dimensional numerical results of the improved model and the original model are compared in the same simulation conditions. It is demonstrated that the fin shape and the slotted position have influence on heat transfer rate, average pressure drop and resistance coefficient; two-way slotted fin, which is front sparse and behind intensive, can make the heat transfer rate improve about 11.8% and the pressure loss rise about 15.7% when the frontal velocity is 5 m/s; the rotary type of fin with double-ear structure can make heat transfer rate increase by 8.28% and pressure drop only increase by 0.25%—0.83% when Re=2 400—8 400, which has the best comprehensive performance, hence provides a beneficial reference for the fin design of the fin-and-tube heat exchanger.