The invention provides a speed reducer box of a stirrer, and relates to the technical field of stirrer reduction boxes. The speed reducer box of the stirrer comprises a speed reducing base body and adriving motor, wherein a control cavity is formed in the speed reducing base body, a driving rotating shaft is rotationally connected to the top of the inner cavity of the control cavity, a first gearis fixedly installed on the surface of the driving rotating shaft, a linkage rotating shaft is rotationally connected to the top wall of the inner cavity of the control cavity, a second gear is fixedly installed on the surface of the linkage rotating shaft, and the left side of the second gear is meshed with the right side of the first gear. According to the speed reducer box of the stirrer, whenthe speed reducer box is installed, the output end of the drive motor is fixedly arranged on the surface of the screw rod in a threaded mode, so that a first screw cap locks a second side plate and asecond screw cap locks a first side plate, then the speed reducer box is more accurate and fast to install, the operation is simple, the structure is compact, processing and recycling are easy, the speed reducer box and the stirrer are convenient to assemble and disassemble, so that the speed reducer box is convenient to maintain.