The invention relates to an assembling and manufacturing method of bottom layer components of a large-size polyurethane insulation box for an LNG ship. The method includes the following procedures ofa code scanning procedure, a feeding procedure, an automatic gluing procedure, a bottom layer component assembling procedure, an RSB assembling procedure, an RSB rolling procedure and an overall correcting procedure after assembling. Compared with the prior art, the assembling and manufacturing method of the bottom layer components of the large-size polyurethane insulation box for the MARK III type LNG ship is designed, manipulators or robots are used for automatically completing feeding, gluing and assembling of a bottom layer polyurethane board, a bottom layer veneer and an RSB, overall correction after assembling is achieved, the phenomena of misalignment and the like caused by manual assembling are greatly reduced, production efficiency is improved, and high-precision quality requirements of products are met.