The thermal insulation material prepared by sodium silicate has many advantages such as incombustibility, light weight and low thermal conductivity, but the poor water resistance restricts its application. Therefore, sodium tetraborate was chosen as the modifying agent and added into sodium silicate solution to prepare thermal insulation material by low temperature sintering. The chemical structure and physical properties of the material were characterized and ion leaching experiments were carried out to investigate the effects of sodium tetraborate. The results show that sodium tetraborate can effectively reduce the number of -OH groups in the material, and make Si-O structure more complex, which can improve the water resistance of the material. When the content of sodium tetraborate is 1% (mass fraction, the same bellow), it has the most significant inhibitory effect on the leaching of sodium ion and silicate ion in the material, and the ion concentrations of the two are reduced by 65.33% and 45.02%, respectively. When the sodium tetraborate content is 3%, the softening coefficient of the material is increased by 84.6%, and its compressive strength, thermal conductivity and apparent density are 0.46 MPa, 0.046 W/(m·K) and 123.1 kg/m3, respectively.