Hot and humid working environments exist in civil engineering, exploration, shipping, and so on. Especially in mines and textile workplaces, the air humidity is usually close to saturation. Frontline workers perform physically demanding work, which will make the body sweat greatly and increase the occurrence of heat-related illnesses. The microenvironment under clothing can be improved by a ventilation cooling vest with pressurized air (denoted VCV), and the trunk skin temperature will be decreased. However, the amount of heat that a VCV removes from a working human body in hot and humid environments is unclear. In this study, human experiments were carried out, the ambient temperature was controlled at 30 degrees C, 32 degrees C or 34 degrees C, and the air humidity was 90%. The subjects wore a labor suit (denoted LS) or a VCV, running on a treadmill at 5 km/h or 7.5 km/h. The results showed that the total trunk heat loss was increased by 169-237%, and the cooling power of the VCV was between 79.5 and 97.6 W when wearing the VCV. However, the actual skin wettedness is often less than the calculated value, and the calculated cooling power should be considered the upper limit. The study indicated that the cooling capacity of the VCV increased as the ambient temperature and labor intensity increased, and the heat dissipation of the body also increased.