Owing to limitations such as low speed and low accuracy in the detection system for visible foreign substances in oral liquids of traditional Chinese medicine (TCM) of an assembly line, a high-speed machine-vision based system which can detect multiple bottles of oral liquids simultaneously is designed. The imaging system and the mechanical system are introduced. To effectively eliminate the sloshing of the bottles, an image registration method based on edge extraction is proposed. And a binarization method which implements point-by-point segmentation on images is proposed to obtain high-quality binary images. The experimental results show that the system can effectively detect foreign substances in oral liquids of TCM with high-speed, and meet the requirements of practical assembly lines.