The invention relates to an insulation construction method for a city building, in particular to an indoor insulation construction method for cave dwelling type environment of the city building, and solves the problem that no mature indoor insulation construction method exists at present. The method comprises the construction working processes of substrate treatment, wall surface construction, ceiling construction, bathroom wall surface construction, and floor slab floor construction; through high-performance insulation material and unique construction technology, the invention performs the insulation treatment to the four indoor walls, the four walls of the bathroom, and the ceiling and the floor, can enable the indoor environment to form an insulation environment similar to an inner liner of a thermos bottle, can maintain the indoor temperature fluctuation within a very small fluctuation range, creates a cave dwelling type indoor environment with cool summer and warm winter, not only effectively prevents the cold and hot bridge phenomenon, but also meets the heat insulation requirement in a house, and achieves an energy-saving effect. On one hand, the invention technically guarantees the effective operation of family heat metering, on the other hand, the environmental effect created by the invention is basically similar to the thermal environment of the cave dwelling.