【Objective】 Extensive regions of purple soil are afflicted by acidification, whereas calcareous purple mudstones, distinguished by their alkaline pH, abundant mineral composition, and low heavy metal content, are theoretically well-suited to ameliorating acidic purple soil in their vicinity. 【Method】An 80-day laboratory incubation experiment was conducted to evaluate the effectiveness of calcareous purple mudstones in ameliorating acidic purple soil. The geological ages of the two parent rocks were the Jurassic Shaximiao Formation (J2s) and the Jurassic Suining Formation (J3sn). 【Result】The findings revealed that both purple mudstones effectively neutralized soil acidity, enhanced soil potassium content and, increased potassium bioavailability, and reduced the bioavailability of heavy metals. These mudstones offer a promising solution for improving acidic purple soil, thereby promoting soil health and fertility. Compared to J2s mudstone, J3sn mudstone exhibited a superior overall improvement effect on acidic purple soil due to its richer calcium content. (1) When J2s mudstone was added to acidic purple soil at rates of 2%, 5%, and 10%, the soil pH increased gradually from 4.73 to 4.93, 5.30, and 6.27, respectively. Concurrently, the soil exchangeable acidity decreased from 2.84 cmol·kg-1 to 2.79, 1.40, and 0.70 cmol·kg-1, respectively. Differently, when J3sn mudstone was added at the same rates, the pH of the acidic purple soil increased significantly to 7.20, 7.87, and 8.00, achieving neutral to alkaline levels. Notably, no exchangeable H+ or Al3+ was detected in the soil after the addition of J3sn mudstone. Additionally, the addition of both mudstones resulted in an increase in soil exchangeable Ca2+, effective cation exchange capacity, and base saturation. (2) Overall, the addition of both J2s and J3sn mudstones to acidic purple soil resulted in a gradual increase in the contents of rapidly available potassium (K), slowly available K, and total K. Specifically, after an 80-day incubation period, the proportion of soil available K to total K increased from 1.58% to 1.76%, 1.88%, and 2.08% with the addition of 2%, 5%, and 10% J2s mudstone, respectively. In comparison, the addition of J3sn mudstone at the same rates led to a more significant increase in the proportion of available K to total K, reaching 1.91%, 2.01%, and 2.24%, respectively. (3) The addition of purple mudstones did not significantly increase the content of total heavy metals (Cu, Zn, Ni, Pb, Cd) in soil, but it significantly decreased the available heavy metal content in proportion to the total content. This reduction was more pronounced with the addition of J3sn mudstone compared to J2s mudstone, indicating its superior passivation effects on heavy metals in acidic purple soil. 【Conclusion】Given the widespread availability, cost-effectiveness, ease of crushing, and convenience of application of calcareous purple rocks in regions where purple parent rocks are naturally exposed, they offer a practical solution for improving acidic purple soil. It is recommended that, under field conditions, 15~45 tons per ha of J3sn mudstone or 75~120 tons per ha of J2s mudstone should be applied to ameliorate acidic purple soil. By leveraging these mudstones, farmers and land managers can efficiently ameliorate acidic purple soil, thereby promoting soil health, crop yield, and overall ecosystem resilience.