An influence function method has been developed to analyze stress intensity factors, K, for surface cracks, which are subjected to arbitrarily distributed surface stresses. The method has been applied to the analysis of a series of influence coefficients for flat plates with a semielliptical surface crack. It has been shown, based upon the data of the influence coefficients, how easily the K-values for a semielliptical surface crack in a flat plate, with arbitrary aspect ratio and depth to thickness ratio, can be evaluated against arbitrarily distributed surface stresses.