In order to understand the indoor thermal environment of cave dwellings in summer,three types of caves including the free-standing,the cliff-sided and the underground were selected for research and testing,which were compared with local brick farmhouses for analysis.Thermal environment parameters such as outdoor and indoor air temperature,relative humidity and wall surface temperature in summer were studied.The results show that the indoor thermal environment of cave dwellings is better than that of briick farmhouses.The indoor temperature fluctuation of cave dwellings is small,the relative humidity is high,and the thermal environment basically meets the requirements of human thermal comfort.By analyzing the role of the spatial layout and the thermal performance of the envelope in creating the indoor thermal environment of the cave dwelling,the study found that the relatively closed space of cave dwellings and the large thermal inertia of the heavy envelope structure can effectively resist the outdoor temperature fluctuations,thus keeping the temperature of the inner wall stable,which is the main reason for the"cool in summer"of cave dwellings;The underground caves have lower indoor air temperature due to the small window-to-wall area ratio;the cliff-side and underground caves have thicker soil layer in the enclosure structure,which has strong water storage capacity and greater indoor relative humidity.The research can provide theoretical support for the transmission of ecological experience of cave dwellings on the Loess Plateau and the construction of new dwellings.