Abstract: Based on the cleanliness of the transmission system of the continuously variable transmission tractor, a systematic method for tracing the source of particulate pollutants is established in this research.The processes of particulate matter extraction, sample preparation, selection of test conditions, scanning electron microscope/energy spectrum and spectral classification analysis, result statistics and judgment are described in detail.Several transmission systems are analyzed, and the source of pollutants is traced, it can reflect the manufacturing process that need to be aimed at improving cleanliness, and has guiding significance for production.