Silica aerogel has a broad application prospect in the field of thermal insulation due to its very high porosity and very low thermal conductivity.Tthe change of thermal conductivity of silica aerogel under different temperature heat treatment conditions was studied,and the related mechanism was explained on the basis of microstructure evolution.With the increase of heat treatment temperature,the thermal conductivity of aerogels first decreases and then rises.When the heat treatment temperature was lower than 400 ℃,the thermal conductivity of the aerogel decreased as the heat treatment temperature increase.This is because the lower temperature heat treatment removes most of the impurities inside the aerogel and makes the internal pore structure more uniform.When the heat treatment temperature was at 400~700 ℃,the higher temperature made the pore diameter inside increase significantly,and the aerogel particles increase,so that the thermal conductivity increased with the heat treatment temperature increase.When the heat treatment temperature was higher than 700 ℃,the aerogel particles began to sinter,the skeleton structure collapsed,the density increased remarkably,and the thermal conductivity also rised sharply.At this time,the typical characteristics of aerogel lightweight porous were not available.It is considered to have expired.Results showed that some guidance for the application of hydrophilic aerogel:the aerogel will have a best thermal insulation performance when treatment at 400 ℃ for a period of time.The aerogel′s working temperature should be below 700 ℃,and increase of temperature will slightly decrease the thermal insulation capacity of the aerogel;The aerogel will lose its thermal insulation capacity at temperatures above 700 ℃,so it should not be used at this temperature.