To let an infrared thermal imager measure the temperature of micrometer-level heating structures in micro-electronic devices accurately and overcome the problem of device deformation due to expansion and contraction, a single-temperature emissivity measurement method is proposed. The influence of expansion and contraction on the detection result when a traditional dual-temperature emissivity measurement method is used to detect micro-electronic devices is analyzed. In the process of temperature transformation, the deformation effect of the device may affect the measurement result seriously. The proposed single-temperature emissivity measurement method is designed for the microscopic infrared test of micro-electronic devices. It can measure the emissivity of a device as long as it is kept at a fixed temperature. The theoretical analysis result shows that the single-temperature method and the dual-temperature are equivalent in the final measurement results. However, the single-temperature method can avoid the deformation of devices. So, the accuracy and reliability of its measurement result is ensured.