A method for detecting bottled liquor impurities based on machine vision was introduced. In order to extract small detection targets from a complex image, an inverted flipping detection method was designed. A high-resolution digital video camera was used to acquire the video sequence of the bottled liquor. After that, an improved seconddifference method was utilized to detect possible tiny moving targets in the liquid. Morphological characteristics of the bubbles and visible impurities were used to estimate whether the liquor contains impurities. The experiments demonstrate the effectiveness of the proposed method.