Abstract: A novel algorithm based on the primary and secondary ridges within the fingerprint block was proposed for the orientation field estimation. The algorithm comprises four steps: preprocessing original fingerprint image, determining the primary and secondary ridges of fingerprint foreground block using the top semineighbor searching algorithm, estimating block direction based on straightline model of such a primary ridge and correcting the spurious block directions. The experimental results show that it achieves satisfying estimation accuracy with low computational time expense. A further experiment shows that it is more accurate and robust to noise compared with the previous methods and can improve the performance of a fingerprint recognition system.