The invention belongs to the field of metallurgical equipment, and in particular relates to a whole-body type external-heating muffle type rotary kiln. A whole-body type continuous external heating muffle type coal-based rotary kiln device with a preheating section and a high-temperature section is adopted, the continuous stabilization of the temperature in a high-temperature area is realized, and a strict requirement on a reduction condition of reduced iron is met. By adopting a muffle-type heating mode, a reduction atmosphere in the rotary kiln is very full, the volatile gas is totally recycled, and the afterheat is fully utilized, so that the required reduction temperature of reduced materials can be greatly reduced, the reduction speed is greatly increased, the energy consumption is greatly reduced, and the carbon emission is reduced; by using non-caking coals with high granularity and high quality as reducing coals, the device is suitable for various iron raw materials with high grade, low grade and varieties, the reduction process is flexible, and the device has many advantages. According to a single production line of the device, the annual reduction treatment ore quantity can reach the maximum scale of 1,800,000-2,100,000 tons.