1. A method for extracting fingerprint feature data using a ridge orientation model, comprising the steps of: a) scanning a fingerprint of a person requiring fingerprint recognition with a fingerprint acquisition device, and converting the fingerprint into a digital fingerprint image of predetermined format; b) dividing the fingerprint image into a plurality of regions, each with a predetermined size, and calculating ridge orientations in the regions; c) calculating qualities of ridges according to regions and separating the fingerprint image into a fingerprint region and a background region according to the calculated ridge qualities; d) evaluating and extracting positions of a core and a delta in the fingerprint region and determining the positions of the core and the delta within and outside the fingerprint region from the extracted positions of the cores and deltas; e) setting the determined positions as initial parameters of an initial ridge orientation model for the core and delta; f) calculating a ridge orientation function by calculating parameters with a minimum error between ridge orientation values of the ridge orientation model and ridge orientation values of regions with quality higher than a threshold; and g) calculating ridge orientation values in all regions using the ridge orientation function, and deciding and extracting the positions of the core and the delta from the parameters for core and delta of the ridge orientation function.