Under low-level-light, the invisible video images of network monitoring present the problems of low contrast and less gray information, so a method of normalized transformation is proposed based on human visual, which is inserted into the video network monitoring system based on ARM. Compared with other image enhancement methods, this algorithm can efficiently improve the contrast resolution of the image and reproduce the invisible video images, obtaining clearer and better visual effect. Meanwhile, this algorithm can meet the demand of real-time network monitoring.