The purpose of this paper is to adopt CMOS image sensors to achieve a real-time obstacle avoidance system for wheeled mobile robots, so that the robot can continually detect surroundings, avoid obstacles, and move toward the target area. In this study, CMOS image sensor was used to detect small obstacles and obtain information concerning the environment in front of the robot. In order to avoid obstacles, the rolling speed and direction of the robot's left and right wheels were determined by the image channel weighting parameter method proposed in this study. The experimental results verified that image captured by a CMOS image sensor of the obstacle avoidance system of the wheeled mobile robot, which is combined with an ATMega162 embedded microcontroller, helps the robot avoid obstacles and reach the target area.