This paper is to highlight a concept for computer aided navigation system that uses fluoroscopic image as a basis for real-time surgical tools navigation. Unfortunately, the inherent distortion of the fluoroscopic image deteriorates the quality of surgical navigation. Combing with global and local correction methods, a novel approach for distortion correction is proposed which allows good image quality in relatively acceptable time. A linear cone beam projection model is setup, and the associate transformation that models the actual X-ray projection is calculated.