Inert gas distribution has a great influence on the inerting effect, especially for the multiple-bay fuel tank. In order to find out the optimal scheme, an optimization method based on the entropy-weight improvement TOPSIS method is proposed, and an experimental system of inert gas distribution is established to measure the speed index and uniformity index. The results show that the position of the inlet and outlet has a significant effect on the overall inerting effect. The inerting scheme designed by the entropy-weight improvement TOPSIS method can not only reduce the flow demand of inert gas but also make the oxygen distribution more uniform. The optimization inerting scheme of the Boeing 747 aircraft has improved the average speed index by 3.01% and the average uniformity index by 26.18%. The smoke visualization experiment also showed that the scheme designed by the entropy-weight improvement TOPSIS method has the denser white smoke, which means that the scheme has better performance.