A thermal insulation construction process for restricted space of a liquefied natural gas plant comprises the following steps of firstly, confirming the collision positions of a pipeline or a facility; secondarily, arranging a thermal insulation tank; thirdly, installing several layers of aerogel and carrying out sealing; fourthly, installing lap joint position aerogel at the bottom of the tank; fifthly, repeating the operation of the fourth step and accomplishing installation of aerogel at the lap joints of ladder end openings of a thermal insulation tank opening; sixthly, infiltrating metal sealants to seal the lap joints of stainless steel outer protection plates; seventhly, detecting the appearance and finishing the whole construction process. By partial grooving and installation of thermal insulation materials with a thermal insulation effect, the problem that the installation distance of thermal insulation materials between the pipeline and the facility is too small or the problem of thermal insulation treatment in some restricted space is solved; furthermore, prefabrication can be carried out in a workshop according to sizes, site prefabrication cost is reduced, and construction difficulty is lowered; meanwhile, the appearance after installation is beautiful.