Two important concepts, which are "Equivalent Distributed Stress" and "Representative Surface Crack", for applying FLARP to the fatigue crack initiation and growth simulation are introduced in this paper. Equivalent distributed stress corresponds to the distributed stress in an infinite plane with a straight crack for which the relationship between the crack length and the stress intensity factor is the same as in the considered cracked body. The stress is proposed in order to prevent the numerical simulation of crack opening/closing for a surface crack. Representative surface crack corresponds to the single surface crack replacing plural surface cracks generated at the sound stress concentration site. This concept is introduced in order to prevent direct crack growth simulation for plural cracks.