Abstract. In this paper the hot steel work environment is simulated and a thermal manikin is utilized to evaluate the thermal adjusting effect of a cooling vest incorporated with PCM packs of gel. Two control modes of the thermal manikin, the constant energy input mode and the constant skin temperature mode are used respectively to evaluate the cooling vest’s thermal adjusting effect. The experiment demonstrates that the cooling vest can alleviate the manikin’s skin temperature. When the constant energy input control mode is used, the manikin’s body parts covered by PCMs have lower skin temperature than other body parts; When the constant skin temperature mode is used, the manikin’s chest and back part, followed by the abdomen and buttocks part have the highest energy cost.