1. Clean the mung bean impurities, put them in a pot and soak them in cold water (warm water in winter, twice as much as mung beans) for more than ten hours. When rubbing the bean skin by hand, take it out and add water to grind it into a thin paste (the finer it is, the better). The thin paste is about 2.65 kg per kg of mung beans. Then, add 1.5 kg of slurry water (that is, clear water skimmed from bean juice and starch before) to the dilute paste, and add not less than 12 kg of cold water for filtration, and about 17 kg of slurry and 2 kg of bean dregs can be filtered out. 2. Pour the slurry into a vat and let it stand overnight. White starch precipitates to the bottom of the vat, with a layer of grayish brown black powder on it, a layer of raw bean juice with grayish green color and sticky texture on the bottom, and floating foam and slurry on the top. Skim the froth and slurry, take out the raw soybean juice (about 8 kg raw soybean juice, about 500 g starch and a small amount of black powder), precipitate again before cooking, and precipitate for six hours in summer. It will precipitate all night in winter. After settling, skim off the mud on it. 3. Put a little cold water into the pot, bring it to a boil, and then pour in the raw bean juice. When the bean juice gradually rises out of the pot, immediately switch to low fire to keep warm (high fire can't be used at this time, otherwise it will turn into hemp tofu one by one), and serve with spicy pickles.