In this paper, a new system of visual detect line robot based on CMOS image sensor was designed. Meanwhile a new technology to detect line was proposed and designed. The system includes nuclear module, image collecting module, robot orientation module, electromotor drive module, man-computer interaction module and power supply module. The principle, function and implementation of every module were introduced in detail. Results of experiments show that the system has not only strong real-time capability and high accuracy, but also outstanding stabilization.