Abstract: Foam extinguishing system used in fixed-roof tank is divided into 3 types, that is, above-liquid foam extinguishing system, under-liquid foam extinguishing system and semi-liquid foam extinguishing system. However, obvious defects can be seen in this 3 existing foam extinguishing systems, and for the 1st system, it is easily damaged with lower putting out efficiency; for the 2nd system, it easily pollute the oil stored and higher pump is needed; for the 3rd system, it can not be reused with higher cost of building. A new type of foam extinguishing system is provided in this paper. The new system is manufactured with simple structure, low construction cost, high putting out efficiency, low operation and maintenance costs and high performance-price ratio, with great popularization value.