The invention belongs to the field of structural sealing and particularly relates to a double-layer sealing structure and a sealing method for aircraft optical cabins under high-pressure-difference conditions. The double-layer sealing structure comprises a bottom plate and a cover, and the cover covers the bottom plate to form a sealed cabin. Two annular seal grooves are formed in a surface, contacting with the cover, of the bottom plate. An external first annular seal groove is filled with high-temperature vulcanized silicon rubber to form a first sealing structure, and an internal second annular seal groove is filled with high-vacuum seal silicon grease to form a second sealing structure. The first sealing structure is capable of realizing airtight sealing under high-pressure-difference conditions and capable of realizing moisture isolation. After hermetical assembly is finished, gas replacement is performed in a high-temperature environment, moisture of internal parts and moisture of high-temperature vulcanized silicon rubber can be drained to meet an airtightness requirement under certain high-pressure-difference conditions.