Thermal manikin is a system of simulating figures and heat states of human body. Present thermal manikin is always enclosed by hard materials, and not covered with surface coating. So the surface condition of thermal manikin is very different with real body, which reduces thermal manikin's repeatability. Therefore the research on thermal manikin's surface coating and its effect on thermal manikin's repeatability are necessary. In this paper, an appropriate material was selected to be thermal manikin's surface coating and the satisfying result in improving the repeatability of thermal manikin was achieved. Firstly, five kinds of candidate surface coating materials were selected, which were HTV, EVA, TPU, natural rubber latex and cotton fabric. To evaluate the synthetic performance of these materials, parameters characterizing material's mechanical and thermodynamic properties were achieved by series of experiments. Meanwhile, fuzzy mathematic theory was employed to do data analysis, which showed that HTV had satisfying optimization performance and can be used as thermal manikin's surface coating. Finally, to verify the function of HTV surface coating in improving thermal manikin's repeatability, comparative repeated experiments were performed in climate chamber when thermal manikin covered with HTV surface coating and did not cover with HTV surface coating. Results show that HTV surface coating can improve the repeatability of thermal manikin obviously.