This study reports the subjective perceptions and mental state of employees working in the Erdaogou Mine, affiliated with Jiapigou Minerals Limited Corporation of China National Gold Group Corporation (CJEM); these employees are pioneers working at the deepest point below ground in China. The data represent a valuable baseline from which to assess the effects of the environmental factors in the deep-underground on human physiology, psychology, and pathology.The air pressure, relative humidity, temperature, total γ radiation dose-rate, and oxygen concentration in the CJEM in the aisles in goafs at 4 depths below ground were measured. Study subjects were administered a study-specific questionnaire that included items that targeted factors with potential to affect respondents' health and wellbeing and included the symptom checklist-90-revised (SCL-90-R).Air pressure, relative humidity, and temperature rose, total γ radiation dose-rate decreased, and there was no change in oxygen concentration with increasing depth below ground. Most (97.2%) respondents had a negative impression of the ambient conditions in the deep-underground space. The most commonly perceived adverse factors included moisture (74.9%), heat (33.5%), and poor ventilation (32.4%). 93.29% of respondents associated ≥1 self-reported negative physical symptom with working in the deep-underground space; the most frequent symptoms were being easily tired (48.7%), tinnitus (47.5%), and hearing loss (44.1%). Higher SCL-90-R scores were associated with the perception of >1 adverse factor in the deep-underground, spending >8 hours continuously in the deep-underground space, or working at a depth > 1000 m below ground. >1 perceived adverse factor in the deep-underground and continuously spending >8 hours in the deep-underground space were significant predictors of high SCL-90-R scores.Adverse factors, including high temperature, humidity, and dim light, may have negative impacts on the physical and psychological health of people who spend long periods of time living and/or working in the deep-underground space.