According to the requirements of flame retardant and environmental protection of wool fabrics, a phosphorus- nitrogen intumescent flame-retardant (IFR) system was constructed on the surface of wool fabrics based on dip-rolling-drying process with DEA serving as carbonizing agent, phosphorous acid and phosphoric acid used as acids, and urea serving as blowing agent. Ammonium N-ethoxy-n-methylene phosphonate-n-ethyl phosphate (ANPP) was designed and the treated wool fabrics with a weight gain (WG) of 27.4% presented highly flame retardancy and exhibited a high limiting oxygen index (LOI) of 37.8%; after 50 laundering cycles (LCs), LOI can still be remained at 30.5%. Self-extinguishing properties in the vertical combustion. The cone calorimeter (CONE) test verified that the peak heat release rate (PHRR) of the untreated wool fabrics declined to 82.2 from 251.7 kW/m2 after ANPP treatment, and the total heat release (THR) was reduced to 4.4 from 37.9MJ/m2. In addition, the physical properties were maintained in the usable range. The flame-retardant mechanism analysis showed that the dense phosphorus-nitrogen char layer shaped effectively prevented the release of heat and spread of flammable volatile substances in the condensed phase. This study supplies novel ideas on devising and manufacturing of environmentally friendly treated wool fabrics with superior flame retardancy, durability, and high efficiency.