The invention discloses a waste incineration system and a waste incineration method utilizing catalytic combustion to prevent low-temperature synthesis of dioxin. The waste incineration system comprises a waste incineration furnace, a high temperature heat exchanger, a high temperature dust remover, a catalytic combustion device, a low temperature heat exchanger and a flue gas purifying device; flue gas discharged through waste incineration is cooled by the high temperature heat exchanger and then passes through the high temperature dust remover to remove most of solid-state substances including dust, carbon particle and the like so as to remove a catalyst for low-temperature synthesis of dioxin; the purified flue gas enters the catalytic combustion device; the carbon particles and carbonaceous organic material in the flue gas are converted into carbon dioxide and water through catalytic combustion to eliminate the carbon particles and carbonaceous organic material needed by low-temperature synthesis of dioxin; within the dioxin low temperature synthesis range of 200-400 DEG C, the flue gas lacks the catalyst, the carbon particles and carbonaceous organic material needed by low-temperature synthesis of dioxin, so that low-temperature synthesis of dioxin is effectively prevented to reduce pollution to the environment caused by waste incineration.