The LNG tank insulation technology is one of the key technologies in LNG ship building. We developed our own insulation system, called “Kawasaki Panel System”, for a large LNG ship with spherical tanks, and applied this system to our first built LNG ship “GOLAR SPIRIT”. In her unprecedented cooling test using LN₂ and gas trial, it was verified that the performance required for LNG tank insulation was satisfactory and that “No Cold Spot” criterion we aimed at was fulfilled. This paper summarizes the development of our insulation system, describing the outline of the major large scaled model tests carried out to select insulation materials and insulation system and to grasp the thermal efficiency, strength and workability of the system as a whole, and also referring to the specifications of the system determined through these tests and to the outline of the quality control established.