The grain boundary (GB) with an internal barrier layer capacitance (IBLC) effect is the primary contributor to the high GB resistance of CaCu3Ti4O12 (CCTO) materials, which also directly determines their colossal dielectric properties. This paper investigates the effects of the thermal shock numbers and temperatures on the dielectric properties of CCTO materials. The findings indicate that increasing the thermal shock numbers can diminish the GB resistance and thus enhance the dielectric constant. Moreover, increasing the thermal shock numbers can reduce the dielectric loss in the low-frequency region, reducing the dielectric loss at 20 Hz from 0.195 for the NC1 sample to 0.095 for the NC6 sample, a reduction of approximately 51 %. In addition, increasing the thermal shock temperature improves the frequency stability of the dielectric constant in the high-temperature region by changing the GB resistance, although the dielectric constant decreases. Importantly, this thermal shock approach improves the dielectric properties of CCTO materials by affecting the ceramic GBs, which is instructive for studying the properties of other GB-dominated materials.