Abstract: How much energy the use of the straw-based building insulation material（SBBIM） in question might save annually was calculated and how much CO2 emission might be reduced by the use was estimated against the heat the burning of the equivalent amount of straws might release.A comparison analysis was conducted of SBBIM and expandable polystyrene（EPS） in energy consumption,CO2 emissions and economy during their production processes.Used as building insulation,straw could save as much as 51 MJ·kg-1·a-1,significantly higher than the energy it released as fuel（7.1～16.7 MJ·kg-1）;if 100 000 rural households in North China are to use the SBBIM,it may reduce CO2 emission by 16 million tons or more in 10 years.Being the same in heat insulation effect,SBBIM consumes less energy and emits less CO2 than EPS in production,but overmatches EPS in economy.It is,therefore,concluded that it is advisable to extrapolate the technology of using straw as building insulation material in the broad rural area of North China.