The Urban Heat Island (UHI) effect has led to the deterioration of the thermal environment in high-density old neighborhoods. However, current studies on outdoor thermal comfort evaluation in communities still face issues such as a relatively singular evaluation dimension, unclear correlations between quantitative indicators, and a lack of in-depth comparison of typical spatial differentiation within communities. Taking Shentian Community, a high-density old community in Xiamen City, as the research subject, a multidimensional evaluation scheme of microclimatic factors, subjective and objective thermal comfort, and crowd activities was constructed, based on on-site measurements, questionnaire surveys, and correlation analyses, focusing on the nuances of outdoor thermal comfort in the complex spaces of old communities. The quantitative relationships and influence mechanisms among these factors were also analyzed, and a more accurate baseline heat stress scale was established. The results showed that (1) the neutral Physiological Equivalent Temperature (PET) in the high-density community in Xiamen was 23.14℃, and the corresponding PET value for the “comfort” tier was ≤29.53℃. Under different space types, there are more obvious differences in the physiological equivalent temperatures required to cause changes in TCV and TSV; (2) the degree of influence of each meteorological factor on the Thermal Sensation Vote (TSV) and on the Thermal Comfort Vote (TCV) were different, and global radiation was the main factor influencing subjective thermal comfort; (3) space occupancy can better characterize the overall community thermal comfort in hot and humid areas, and for every 1°C increase in PET, the overall Usage Rate (UR) of the outdoor space in the neighborhood will decrease by about 2%. However, the tolerance thresholds and sensitivities of residents" willingness to use space in response to changes in thermal comfort vary across different space types in older neighborhoods. The results of the study enhance the systematicity and applicability of the coupled subjective-objective thermal comfort analysis, improve the precision of quantitative characterization of thermal comfort at the community scale, and provide important scientific support and decision-making basis for community planning and renewal practitioners to improve the thermal environment of outdoor spaces.