Rational insulation structure design plays a crucial role in the performance of Liquefied Natural Gas(LNG) double metal wall full containment tanks. The calculation of condensation temperature is a key aspect of this design process. Therefore, it is necessary to conduct thorough research on condensation temperature calculation and insulation structure optimization for these tanks. This study focuses on an existing 15 000 m³ LNG double metal wall full containment tank as a case study. The research methodology includes clearly defining the calculation method for the condensation temperature on the outer surface of the tank in accordance with requirements of relevant standards, conducting both qualitative and quantitative analysis on the thermal corner protection area, which is particularly prone to condensation, proposing optimization suggestions for the tank bottom insulation structure design based on the calculation results. The primary objectives of this research are to minimize the possibility of condensation phenomenon, to ensure the safety and economic viability of operation and maintenance, and provide guidance for future design and construction of insulation structures in LNG double metal wall full containment tanks.