The invention provides a preparation method of an 
agaricus bisporus low-salt soybean sauce. The preparation method comprises the following steps of putting soybeans after being subjected to cleaning and 
impurity removal into room-temperature water, performing soaking, and performing draining; cooking the drained soybeans until the soybeans are completely cooked; sufficiently and uniformly stirringheated flour with the cooked soybeans when the flour is hot to obtain 
mixed materials; after the 
mixed materials are cooled, performing 
inoculation with 
aspergillus oryzae mother starters, and performing culturing until 
starter materials are yellowgreen so as to obtain finished starters; and taking 
agaricus bisporus 
powder or an extraction solution thereof, mixing the taken 
agaricus bisporus 
powder or the extraction solution thereof with the finished starters to obtain a mixture, putting the mixture into a fermenter for 
fermentation, wherein the 
fermentation period is 7-10 days, then adding microzyme and 
lactic acid bacteria, setting the temperature to be 35-40 DEG C, and continuing performing 
fermentation for 5-7 days so as to obtain the 
agaricus bisporus low-salt soybean sauce. According to the preparation method disclosed by the invention, a low-salt 
solid state fermentation method is adopted, the fermentation time is short, the fermentation temperature is high, growth of infectious microbes is not facilitated, the 
agaricus bisporus low-salt soybean sauce is safe to eat, the soybean sauce produced by the method has the advantages of being healthy, environmentally-friendly, lowin cost and short in 
production cycle, besides, the soybean sauce inherits the advantages of the 
agaricus bisporus, and the soybean sauce obtains favor of consumers.