​When selecting and grading brined nameko mushrooms in drum, it is necessary to use slippery mushrooms that are free of pests and diseases and have normal color as raw materials. Use a sharp knife to remove the aging hard roots, keep the tender handle 1-3cm long, and grade after removing impurities. The diameter of the cap of the first-level mushroom is 1-2cm, without an umbrella, the diameter of the cap of the second-level mushroom is 2-3cm, with a semi-open umbrella, and other foreign products are fully open umbrella mushrooms.