An electrothermal microgripper is an important actuator in microelectromechanical and micro-operating systems, and its temperature field analysis is the core problem in research and design. Because of the small size of an electrothermal microgripper, its microscale heat transfer characteristics are different from those of the macrostate. At present, only a few studies on the heat transfer scale effect in electrothermal microgrippers have been conducted, and the heat transfer analysis method under the macrostate is often used directly. The temperature field analysed and simulated is different from the actual situation. In the present study, the heat transfer mechanism of an electrothermal microgripper in the microscale was analysed. The temperature field of a series of microscale heating devices was measured using microthermal imaging equipment, and the heat transfer parameters of the microscale were fitted. Results show that the natural convective heat transfer coefficient of air on the microscale can reach 60–300 times that on the macroscale, which is an important heat transfer mode affecting the temperature field distribution of the electrothermal microgripper. Combined with the finite element simulation software, the temperature field of the electrothermal microgripper could be accurately simulated using the experimental microscale heat transfer parameters measured. This study provides an important theoretical basis and data support for the optimal design of the temperature controller of the electrothermal microgripper.