The northwest region is located in an arid to semi-arid zone, characterized by a dry climate, significant diurnal temperature fluctuations, and pronounced impacts of temperature and humidity on the crack resistance of loess. While composite stabilized loess has been widely used as road base material, temperature and humidity variations often lead to cracking in the base layer. To address these issues, this study investigates the drying and thermal shrinkage characteristics of composite stabilized loess under temperature and humidity effects. First, a mix proportion design for composite stabilized loess was conducted, with optimal ratios of 6% cement content, 0.02% stabilizer dosage, and 97% compaction degree determined through orthogonal experiments. Two groups of specimens—one with 0.02% stabilizer and one without—were then prepared for drying and thermal shrinkage tests. The dry shrinkage coefficients and thermal shrinkage coefficients of both groups were obtained. By comparing the relationship between dry shrinkage coefficients and time for cement-stabilized soil versus composite stabilized soil, as well as the thermal shrinkage coefficients versus temperature, the drying-thermal shrinkage behavior of composite stabilized loess was established. The results demonstrate that composite stabilized soil incorporating 0.02% stabilizer exhibits superior crack resistance and greater suitability as road base material. This study provides valuable references for future research and holds significant implications for enhancing the performance of road base materials.