The effects of moist heat environment, salt spray and mycete on nano Al₂O₃ thermal insulating materials were studied. The results showed that the thermal conductivity of materials with density of 0.45g/cm³ increased from 0.031 W/(m·K) to 0.047 W/(m·K) at 25℃ after moist heat test. The thermal conductivity of materials rapidly increased from 0.031 W/(m·K) to 0.136 W/(m·K) after salt spray test. The thermal conductivity of materials was kept constant after mycete test. The interaction between the material surface and the test environments was analyzed, and the technology of surface moisture resistence was developed at the material surface. After moisture resistence treatment, the hydrophobicity of the nano-alumina insulating material was significantly increased, the contact angle was more than 90°, and the properties of materials were not affected by moist heat environment, salt spray and mycete.