The utility model provides a double-helical-ribbon screw stirrer, and mainly solves the problems about poor stability and inconvenience in maintenance and disassembly and assembly of the existing stirring device. The double-helical-ribbon screw stirrer is characterized in that a motor (2) is connected with a speed reducer (3); the speed reducer (3) is connected to a frame (1); the upper end of a transmission shaft (4) is connected with the output end of the speed reducer (3), and the lower end thereof is connected with a stirring shaft (5); the stirring shaft (5) is connected with a cross-shaped steady rest (6) through a bearing; the steady rest (6) is fixedly connected to the interior of a curing tank; a shaft sleeve (7) is connected to the exterior of the lower part of the stirring shaft (5) through a spline; a helical ribbon (9) is helically fixed to the outside of the shaft sleeve (7); a helical stirring band (8) is fixedly connected to the exterior of the shaft sleeve (7) through three cross rods (10). The double-helical-ribbon screw stirrer has the characteristics of good stability and convenience in maintenance and disassembly and assembly.