The invention relates to a multifunctional biological solid fermentation tank. The main body structure of the fermentation tank is a horizontal propeller, and spiral auger propeller blades are installed below the tank bottom. An auger is directly communicated with steam for sterilizing form the bottom of the tank and communicated with air for cooling, a spray tube on the upper part of the tank body sprays bacterial liquid for inoculation and can also spray water mist for humidity regulation, and thus, uniform inoculation and humidity control can be realized. The unique tank body horizontal type propeller and the auger coordination system below the tank body are utilized, and the circular flowing and the thorough mixing of a solid material in the tank body during fermentation are realized by controlling the rotating speed and the rotating direction; stirring nonuniformity caused by using a motor to rotate forwards or backwards repeatedly is avoided, automatic material discharge can be realized after fermentation, and material discharge is clean and complete. The operations of sterilization, cooling, inoculation, fermentation, temperature control, humidity control, ventilation, vacuum drying and the like required by solid fermentation can all be completed in the biological solid fermentation tank. The biological solid fermentation tank has the advantages of hardly no bacterial contamination, small occupied space, high automation degree, labor saving, investment saving and the like.