Abstract: Infrared thermography method was used to inspect the defects of exterior walls cement coating under different environmental conditions. The effects of weather conditions, test time in a day and outdoor temperatures on the test results were analyzed, and the suitable conditions in the current technical specifications for defects inspection of exterior walls cement coating using infrared thermography method were modified. The experimental results showed that, the defects of small size were easily to be omitted by mistake in a cloudy day or when the outdoor temperature was lower than 10℃. The method for evaluating the area of bonding defects was proposed based on the image processing of infrared thermography method. The proposed method was effective and quantitative for extracting the area of exfoliation of cement coating. The image processing analysis results showed that, the inspecting result of infrared thermography method was better when at higher outdoor temperature, with larger area and more shallow depth of exfoliation of cement coating. The effect of the thickness of exfoliation of cement coating was not obvious on the inspecting result of infrared thermography method.