The invention discloses a welded seal structure of a shell flange of an air cooler, mainly comprising a shell flange, an end cover, a fastener and a seal element, wherein the seal element is clamped by the end cover after being welded with the shell flange so as to form a flange seal structure under the compacting action of the fastener. The seal structure has reliable seal performance and convenient disassembly, and can be used on occasions at high temperature and under high pressure and occasions in which the medium is inflammable, explosive and high in toxic hazards.