[Objective] The effects of acid rain on the leaching loss of base ions and molybdate ions in purple soil were analyzed in order to provide a scientific basis for understanding fertility changes and nutrient management in purple soil under acid deposition conditions. [Methods] Taking the calcareous purple soil developed from the parent material of the Jurassic Penglaizhen Formation （J₃ p） as the research object， five leaching solution treatments were established to simulate acid rain with pH values of 2.5 （T₁）， 3.5 （T₂）， 4.5 （T₃）， 5.6 （T₄）， and 7.0 （deionized water， CK）. [Results] ① The pH value of the leachate showed a trend of rapid decline followed by gradual stabilization. In the early stage， the pH value of the leachate decreased by 6.17%， 8.05%， 3.75%， 3.70%， and 2.01% for T₁， T₂， T₃， T₄， and CK， respectively. In the later stage， it stabilized within a range of ±0.2 of the pH value of the 10th leachate. After two years of simulated acid rain leaching， the pH value of the leachate in T₁， T₂， T₃， and T₄ decreased by 0.22， 0.39， 0.32， and 0.29， respectively. Compared with the CK， the soil pH value decreased by 0.67， 0.62， 0.56， and 0.46， respectively. ② The contents of base ions in the leachate exhibited a fluctuating decline with increasing leaching cycles， and the total leaching amounts generally decreased as the pH value of the leaching solution increased. The total leaching amounts of K⁺ followed the order： T₁ > T₃ > T₂ > T₄ > CK. The total leaching amounts of Na⁺ followed the order： T₁ > CK > T₂， T₃， T₄. The total leaching amounts of Ca²⁺ followed the order： T₁ > T₂， T₃ > T₄ > CK. The total leaching amounts of Mg²⁺followed the order： T₁ > T₃ > T₄ > CK， T₂. The total leaching loss amounts of base ions were in the order： Ca²⁺> Mg²⁺> Na⁺> K⁺. ③ The Mo⁴⁺content in the leachate showed a fluctuating decreasing trend， and the total leaching amount generally increased with increasing pH value， following the order： CK （59.22 μg） > T₄ （56.11 μg） > T₃ （52.42 μg） > T₁ （41.03 μg） > T₂ （39.56 μg）. Mo⁴⁺ was positively correlated with pH value and negatively correlated with K⁺and Ca²⁺. ④ A synergistic relationship was observed between the leaching loss amounts of base ions and Mo⁴⁺. As the leaching loss of Mo⁴⁺ increased， base ions first increased and then decreased. The total leaching loss amounts of K⁺， Na⁺， Ca²⁺， and Mg²⁺ reached their peaks when the total leaching loss of Mo⁴⁺ reached 46.11， 46.11， 44.51 μg， and 46.11 μg， respectively. [Conclusion] The T₁ treatment of simulated acid rain （pH = 2.5） results in the highest leaching loss of base ions but the lowest leaching loss of molybdenum. The leaching loss amounts of both base ions and the trace element molybdenum in the T₃ treatment （pH = 4.5） are at relatively high levels， indicating more severe nutrient loss.