Water chestnut grows in a special environment and contains some harmful impurities. After picking, clean up the excess old leaves and impurities, put them in clean water, wash them carefully, put them aside and drain. At this time, the water chestnut can not be directly used for cooking, but should also be soaked in salt water for a period of time, with the aim of further cleaning up harmful substances, soaking for about 20 minutes, and then washing with clear water and cooking directly.