Fingerprint is one of the most widely used biometric modality for recognition due to its reliability, non-invasive characteristic, speed and performance. The patterns remain stable throughout the lifetime of an individual. Attributable to these advantages, the application of Fingerprint biometric is increasingly encouraged by various commercial as well as government organizations. Fingerprint feature detection is to automatically and reliably extract minutiae from the input Fingerprint images. However, the performance of a minutiae extraction algorithm relies heavily on the quality of the input Fingerprint images. In order to ensure that the performance of an Fingerprint authentication system to be robust, it is essential to preprocessing Fingerprint image. This thesis describes steps involved during Fingerprint preprocessing, which improves the clarity of ridge and bifurcation structures of input Fingerprint images. After preprocessing minutiae are extracted and stored in database. Further an online Fingerprint authentication system is implemented in which elementary indexing strat- egy is used. Indexing Fingerprint data is done to identify and retrieve a small subset of candidate data from the database of Fingerprint data of individuals. Experimental work show that incorporating the online system, preprocessing algorithm, matching algorithm improves the overall response time