Exogenous CaCO₃ addition, as a common soil improvement and acidification control measure, directly acts on the soil cementation process by supplementing calcium ions and adjusting pH. However, there is still a lack of systematic understanding of its comprehensive influence law and internal mechanism on the distribution characteristics and stability of typical calcareous soil aggregates. In this study, five typical calcareous soils in arid and semi-arid areas of northern China were selected, and the indoor simulated culture of control (straw addition 10 g/kg) and exogenous CaCO₃ addition (straw addition 10 g/kg + exogenous CaCO₃ addition 80 g/kg) was set up to analyze the distribution characteristics and stability of soil aggregates. The results showed that the addition of exogenous CaCO₃ significantly increased the soil CaCO₃ content (BST increased by 84.4% at 30 d), and changed the aggregate size distribution. The specific performance was that the proportion of microaggregates (0.053-0.25 mm) increased, and the proportion of macroaggregates (>2 mm) decreased significantly (SST and LST decreased by 113.0% and 103.1%, respectively).The stability of aggregates showed a time-dependent change : short-term (30 d) addition of CaCO₃ reduced the MWD of FST and LST by 12.5% and 38.5%,respectively ; after long-term (180 d) culture, although its stability has been restored, it is still lower than that of the untreated treatment. In addition, CaCO₃ addition reduced soil pH, and SST decreased by 1.4 % at 180 d. Overall, exogenous CaCO₃ has a staged and type-specific regulatory effect on soil stability by affecting the distribution of CaCO₃ and the reorganization of aggregate structure.