Underground mines are a special type of environment which requires significant attention since they directly relate to miners‟ productivity, health and safety. With coal or ore exploitation into deep underground mine environments, high temperature and humidity creates risks because of large amounts of heat generated from geothermal heat, mining machines, groundwater and mine water. There have been many assessment methods for underground mine environment, such as dry-bulb temperature and wet-bulb temperature. However, none of the current methods can comprehensively evaluate the underground mine environment since most methods consider only one or a few defined factors and neglect others. In order to evaluate the human body‟s thermal status in terms of both personal and environmental viewpoints, this investigation firstly discusses the new upper limits of dry-bulb temperature with the support of some simulated results of indicators from ISO7933, and then adopts both mean skin temperature and dry-bulb temperature to establish a zone diagram. The calculation of mean skin temperature is based on the heat balance of the human body with the ambient environment. Then existent regulations on underground mine environments and some typical condition parameters in underground mines are applied to circumscribe different thermal zones. The established thermal zone diagram defines the preferable condition zone, acceptable condition zone, and prohibited zone. This method considers parameters from both the human body and the surrounding environment and hence offers a more comprehensive estimation.