The reliability of thermal imagery has direct impact on the success rate of user tasks, maintenance costs and life cycle, so its reliability design is increasingly concerned. At the same time, as far as the development of thermal imagery in China is concerned, the reliability of the developed prototype does not reflect the reliability level of the products produced in small batches. Therefore, in order to fully reflect the reliability level of the developed prototype, this paper develops a method for certain infrared thermal imager that analyzes the feature of reliability growth in the development stage. We analyze the faults of the infrared thermal imaging camera, establish the mission reliability model of the infrared thermal imaging camera, propose corresponding improvement measures, and adopts the reliability to verify the effectiveness of the proposed measures. This method meets the requirements of equipment test and appraisal, and can achieve the goal of increasing the reliability of thermal imaging cameras and not reducing the reliability of batch products.