The method of identifying Yves Saint Laurent (YSL) sunglasses is as follows.

1. Through trademark identification, find the brand trademark on the sunglasses and ensure that the shape, size, color and font of the trademark are consistent with the original product. Saint Laurent's trademark is usually "YSL" or "Saint Laurent Paris".

2. Check the label. Genuine sunglasses usually have labels on the temples or inside the frames, which will contain product information, series models and other detailed information. At the same time, Saint Laurent sunglasses will also have the words "Made in Italy" on the label.

3. Look at the material and workmanship. Saint Laurent sunglasses usually use high-quality materials, such as high-quality titanium alloy or Italian acetate fiber. Genuine sunglasses are finely made, free of burrs and imperfections, lightweight and comfortable.

4. Lens identification. The lenses of genuine sunglasses are usually printed with the brand trademark and model number. In addition, the lenses of Yves Saint Laurent sunglasses use high-quality protective lenses that can effectively filter ultraviolet rays.

5. Purchasing channels. Authentic Yves Saint Laurent sunglasses are generally sold at counters or authorized stores. It is recommended that consumers purchase through regular sales channels to avoid buying fakes.