Based on the high penetration rate of mobile devices, reducing power consumption for mobile devices have become increasingly important. In current technology, statistics show that the display of the mobile device dominates the major power consumption of the device (e.g., up to 40% of the total power). Therefore, to efficiently reduce the display power consumption while maintaining the image quality, this paper proposes a novel contrast-aware backlight control algorithm for mobile devices. By transforming the color space for a displayed image from RGB (red, green, blue) to HSI (hue, saturation, intensity), we first calculate the RMS (root mean square) contrast for the image. Then we estimate the "brightness factor" for adjusting the image based on the RMS contrast and the employed HVS (human vision system)-based visual quality assessment technique. At the same time, the estimated brightness factor is used to determine the screen backlight brightness value of the device. As a result, the best tradeoff between the image display quality and the power consumption can be achieved. Our experimental results have demonstrated that 10∼40% reduction of backlight brightness can be achieved, resulting in power consumption of 8∼25%, while good image display quality can be maintained.