Abstract: Addressing the issue of cracking in cement-based materials caused by dry and large temperature difference environments in Northwest China, which significantly impacts the lifespan of concrete structures, this study characterizes the crack sensitivity of cementitious materials under varying environmental conditions using strain abrupt change time in ring-restrained tests. Microscopic observation, computed tomography (CT), and mercury intrusion porosimetry (MIP) were employed to elucidate the mechanisms of restrained shrinkage deformation, cracking behavior, and cracking mechanisms of cementitious materials in dry and large temperature difference environments. The findings revealed that increasing the water-to-cement (w/c) ratio from 0.25 to 0.35 extended the cracking time by 370.59%; a 40% reduction in humidity shortened the cracking time of specimens with a w/c ratio of 0.30 by 20.30%; and a daily temperature difference of 35°C increased the cracking time of specimens with a w/c ratio of 0.25 by 40.63%. Adding 30% fly ash extended the cracking time by 4.41 times. Factors affecting cracking sensitivity were ranked as follows: w/c ratio, fly ash content, and temperature-humidity conditions. Samples with a w/c ratio of 0.25 were most sensitive to temperature changes, while those with a w/c ratio of 0.30 were more sensitive to humidity variations. The results demonstrate that dry and large temperature difference environments exacerbate cracking risks in cementitious materials. Increasing the w/c ratio reduced cracking risks, and incorporating fly ash effectively suppressed cracking, thereby mitigating material sensitivity to cracking. The study also elucidated the mechanisms by which w/c ratio, fly ash addition, and environmental temperature-humidity variations influence pore structure evolution and cracking sensitivity in cementitious materials.