American standard power lines are one kind of the products that domestic wires & cables enterprises produced. Due to their reasonable layout, normative electrical safety design and other advantages, American standard power lines are widely used in United States, Canada, Brazil and other countries and regions. At present, the detection methods that most of the domestic wires & cables enterprises use are manual offline detection and tools detection(such as microscope, projection detector and other traditional equipments,etc). These kinds of method cost large labour with low precision and efficiency,are not applied to mass production. Therefore, a kind of high precision detection method with high speed is needed to meet the requirements of high quality production and high efficiency detection.Taking American standard power lines as the research objects, by using image processing and machine vision knowledge, a set of American standard power line defects detection method based on machine vision was designed. This method has a better effect for American standard power lines on their various defects.