The invention discloses a biological energy fermenting tank with a protection structure. The biological energy fermenting tank comprises a fermenting tank body. The biological energy fermenting tank is characterized in that a reaction chamber is formed in the fermenting tank body; a heat preservation chamber is arranged at the outer part of the reaction chamber; a rotating shaft is arranged at theinner part of the reaction camber; the rotating shaft is provided with a stirring paddle; a filter plate is arranged in a connecting position between the reaction chamber and a lower-end vertebral body; a supporting platform is arranged at the top part of a containing cavity; the supporting platform is provided with a motor; an air inlet pipe is arranged at the inner part of the reaction chamber;a spiral expansion pipe is arranged at the inner part of the containing cavity; the air inlet pipe is provided with an air inlet pipe head. The biological energy fermenting tank disclosed by the invention is simple in structure; promotion of reaction of reactants in the fermenting tank body can be realized through a stirring function of a stirring machine, and the reaction efficiency at the innerpart of the fermenting tank body is increased; through the arrangement of the heat preservation chamber, great action is provided for fermenting at the inner part of the fermenting tank body, a reaction kettle is effectively protected through the action of the spiral expansion pipe during a fermenting process, the use is convenient, and the practicability is strong.