The invention discloses a system for treating waste incineration waste gas. The system comprises an inert gas storage tank, a pressurizing pump, a flame-retardant machine, a thermal ionization chamber with a wall plate made of a heat-insulating material, a 1# electrode, a movable wall plate, a spray nozzle, a cooling system, a plasma reaction chamber, a 2# electrode, a vacuum-pumping device, a heat exchanger, a waste incineration furnace, a pure water slot, a water pump and the like. The waste gas generated by the waste incineration furnace in the system is not required to cooled after being discharged, so that the high-temperature waste gas can provide energy for the reaction through the heat exchanger; through dual effects of ozone molecules and pressurization, the system can generate thermal ionization reaction at a temperature of 800-1000 DEG C, so that the thermal ionization reaction temperature is greatly reduced and the energy consumption is reduced; the thermal ionization chamber of the system is adjustable in size, and a flow range of treated waste gas can be increased to 80000-15000 m<3>/h by adopting a gas compression method, and treatment needs for waste gas of a common waste incineration plant can be met.