The invention discloses sea-buckthorn soybean sauce and a preparation method thereof. The sea-buckthorn soybean sauce is prepared from the following raw materials in percentage by weight: soybean 50-60, flour 30-40 and sea-buckthorn fruit 10-20. The sea-buckthorn soybean sauce is brewed by soaking and 
steaming the soybean, fermenting the flour, 
steaming the flour to make a cake, 
slicing the cake into blocks, performing 
inoculation and 
starter propagation, performing high-salt diluted-state low-temperature 
fermentation, and adding sea-buckthorn sauce in the 
fermentation process. In the invention, a low-temperature ventilation 
starter propagation method is used, so the 
starter propagation time is long, colony propagation is complete, the activity of prolease is high, and more beneficial strains, fragrance and delicate flavors are produced. The steamed 
sponge cake made of the flour is mixed with soybean for starter propagation, so the starter material is loose and rich in 
oxygen and can promote the overall generation of a culture matrix and the enzymes are fully propagated. The production process of the invention adopts a high-salt diluted-state low-temperature 
fermentation technique, wherein the low temperature can prolong the fermentation period; high salt can effectively inhibit the generation of harmful 
bacteria; the yeasts used for fermenting mash have high slat resistance, so the action of 
beneficial bacteria is not influenced; and the diluted state is favorable for the full mixing of the raw materials and the complete fermentation of the mash. The sauce of the invention has a strong fragrance, a good 
flavor and a health-care function.