With global warming and frequent heat waves, the incidence of heat-related-illness has gradually increased, and heatstroke is the most serious clinical syndrome, with high mortality and incidence of sequelae. Effective heatstroke warning aims to reduce the incidence and the harm of heatstroke by monitoring certain parameters and forecasting the possibility of suffering heat illness, however, there is no unified summary of the heatstroke early warning system at present. The occurrence of heatstroke involves two key aspects: climate environment and individual susceptibility, and individual susceptibility is manifested as the difference in heat tolerance ability. This article represents the current early warning system of heatstroke from climate environment, such as effective temperature, heat index, wet bulb globe temperature (WBGT) index, somatosensory temperature, etc., and individual susceptibility, for the reference of research and development in this field.