The invention belongs to the technical field of microorganism bacterium agent fermentation, and particularly relates to a high-density solid fermentation method for agricultural bacillus. The fermentation method comprises the following steps that 1, sterilization treatment is performed on fermentation materials; 2, a fermentation device is sterilized; 3, the fermentation materials in the step 1 are put into the fermentation device in the step 2, and bacillus is inoculated into the fermentation materials; 4, aerated fermentation is performed on the fermentation materials; 5, the fermentation materials are dried. According to the method, the raw materials of a culture medium are simple, choosing range is wide, and the cost is low; the floor space is small, the requirement on equipment is low, special machines and tools are not needed, assembly is convenient, energy consumption is low, and therefore the production cost is much lower than that of liquid fermentation and only accounts for 30%-50% of that of liquid fermentation; compared with pile fermentation and traditional shallow tray fermentation, the fermentation method has the advantages that the requirements for temperature, humidity and ventilatory capacity in the bacillus growth process are taken into account, and the problems such as metabolic heat removal and mass transfer in the bacillus solid fermentation process are effectively solved.