With the increasing volume of sensitive and private information stored in the mobile phone, the security issue of mobile phone becomes an important field to investigate. This paper proposes a fingerprint authentication system for mobile phone security application. A prototype of our system is developed from the platform of BIRD E868 mobile phone with external fingerprint capture module. It is composed of two parts. One is the front-end fingerprint capture sub-system, and the other is back-end fingerprint recognition system. A thermal sweep fingerprint sensor is used in the fingerprint capture sub-system to fit the limitations of size, cost, and power consumption. In the fingerprint recognition sub-system, an optimized algorithm is developed from the one participated in the FVC2004. The performance of the proposed system is evaluated on the database built by the thermal sweep fingerprint sensor.