The utility model discloses a fire fighting exhausting safety access system for buildings. The firefighting exhausting safety access system is based on principles of fluid mechanics and thermodynamics, a fire fighting exhausting safety window is arranged at an uppermost end of a vertical wall or a roof of each room of a building, a branch access which is provided with an upward opening and communicated with the firefighting exhausting safety window is arranged on each firefighting exhausting safety window, the openings of the branch accesses are lower than the lowermost ends of the branch accesses of rooms on each adjacent upper storey of the building, the branch accesses of all rooms of the upper storey and the lower storey are communicated with a main access, an exit of the main access is disposed on the top of the building, and wind caps which move along with the wind are disposed at top ends of the accesses, namely 'chimney effect' known well by everyone in daily living is realized. The firefighting exhausting safety access system can improve evacuation environments for disaster victims and favorable rescue condition for fire fighters, maintains ventilation for 24 hours, is simple in structure and low in cost, and is particularly suitable for modern buildings, and the existing buildings can be modified according to the firefighting exhausting safety access system.