The better focused the image is,the more energy of high frequency it contains. The focusing evaluation function of the auto-focusing system is consistent with the energy of high frequency of the image. The procedure of auto-focusing is to getting the maximum of the focusing evaluation function employing the mountain-climb searching algorithm. Ordinary mountain-climb searching algorithrm is apt to disturbed by local extremum,while optimized mountain-climb searching algorithm can get rid of this disturbance effectively. This paper introduces the principle and realization of the optimized mountain-climb searching algorithm.