Abstract: In order to reduce the heat dissipation losses and save more energy in thermal power plants, by adopting the ultra-low heat dissipation technology, this paper calculates the insulation thickness, heat dissipation reduction, investment increase and investment recovery years of the main steam pipe with the external surface temperatures of insulation structure ranging from 50℃ to 30℃. By taking the newly-built power plant (2×1 000 MW) in Shandong Province for example, the investment in heat preservation is compared with respect to external surface temperatures of main steam pipe of insulation structure at 45℃ and 50℃ . The results show that when the external surface temperature of the insulation structure declines from 50℃ to 45℃, the total volume of the insulation materials will grow, which will cause the increase of the investment by 300 thousand RMB yuan. Nevertheless, the temperature drop at the main steam cycle and the hot reheat steam cycle between the boiler outlet and the steam turbine inlet is reduced by 1 to 2℃ and thus the unit coal consumption is lessened by about 0.6 g/(kW·h). Therefore, substantial economic benefits is achieved for the power plants.