Accurately analyzing the spatio-temporal pattern of impervious surface areas (ISA) and its effect on thermal environments is crucial in urban development planning. This research was aimed to explore the spatio-temporal distribution characteristics and correlation of ISA and land surface temperature (LST) in the built-up areas of Hefei from 2002 to 2017. LST and ISA data were retrieved using radiative transfer equations and the Biophysical Composition Index (BCI), respectively, and their relationship was quantitatively analyzed using multiple model regression. We found that from 2002 to 2017, the total ISA increased by 181.32 km² and expanded from the central to the surrounding area. The Shushan and Baohe districts had the largest expansion area and intensity, respectively. Although the mean value, extreme value, and standard deviation of LST tended to decrease, the proportion of sub-high and high-temperature areas increased considerably. The ISA and LST showed a strong quadratic function relationship, with R²>0.68. LST increased with increasing ISA BCI value, and the average increase in LST was >1ºC for every 0.1 increase in the BCI value of ISA. Our findings can be valuable for urban planning and construction and promote the sustainable development of urban ecology.