Chop a pig's trotters into several pieces, put them in a pot with cold water until the water boils, and take them out to remove the fishy smell. Tetramedulla tetrapanacis, Fructus Jujubae and Fructus Lycii are packed in a gauze bag, and 2500nl of cold water is put into the casserole. The gauze bag is soaked in water for about half an hour. When firing, pig's trotters and soybeans are added at the same time. After the fire is boiled, turn to low heat for 2 hours, and put a little salt when taking out of the pot.