Abstract: Five different three-elements airfoils which contain slat, fix foil and flap were analyzed. The only difference of those three-elements airfoils is the shape of the slat coves, which are faired to five shape, and the cusps are changed with the fairing accordingly. Using the RANS simulation of the in house CFD tool “CCFD-MB”, the relative aerodynamic characters of the coves, such as the Reynolds effects, the stall behaviors, the lift and the drag coefficients, were analyzed. Some of the similar researches done by Boeing and DLR were also mentioned in the document as reference work. The paper indicates some beneficial results: some kinds of the slat coves may lead to negative Reynolds effects; some kinds of cove fairings provide better aero efficiency and potential noise reduction tendency; the normal slat coves wildly adopted in industry design are not the best choices from the point of aerodynamic, yet the aerodynamic characteristic are acceptable. Some suggestions on the choice of slat coves were given according to the consideration of aerodynamic and structure.