Disclosed are a navigation system and a navigation method, wherein the navigation method comprises the steps of sequentially providing image frames containing navigation information and generating electric signals corresponding to a position of an optical sensor, storing a first image frame into a reference frame memory as a reference frame, storing an input image frame subsequent to the first image frame into an input frame memory as a current input frame, setting a mask window having a predetermined size on the reference frame, obtaining correlation values over all the pixels on the current input frame by a full search comparison method, by moving the mask window on the current input frame pixel by pixel, calculating X-axis and Y-axis displacements of a pixel having the greatest correlation value of all the pixels, and updating the reference frame using the current input frame stored in the input frame memory.The navigation system and the navigation method in accordance with the present invention may change input frame selection period based on movement speed of an optical mouse, so that it is possible to detect movement of an optical mouse without changing sampling speed of an optical sensor even when an optical mouse moves fast. Further, the navigation system and the navigation method in accordance with the present invention may consume low power in comparison with a conventional navigation system and method, and reduce noises existed in an optical mouse.