To investigate acidity characteristics at different depths of paddy soil derived from different parent materials, a series of soil samples at different depths were collected from 25 sites with 4 parent materials (red sandstone, river alluvium, quaternary red clay and plate shale) to be determined and analyzed. The results indicated, at 0-20 cm soil layers, paddy soil acidity was larger than that of 60-100 cm soil layers, soil exchangeable calcium (Ca²⁺) and magnesium( Mg²⁺) derived from contents quaternary red clay parent materials were significantly higher than that of plate shale parent material, and there were no significant difference between red sandstone and river alluvium parent materials. Compared with 0-100 cm soil layers, at 20-80 cm soil layers, paddy soil pH increased significantly by 0.54-1.26, exchangeable hydrogen(H⁺) content decreased significantly by 0.12-0.15 cmol/kg, exchangeable aluminum(Al³⁺) content decreased significantly by 1.06-1.38 cmol/kg, exchangeable Ca²⁺content increased significantly by 0.81-2.22 cmol/kg, exchangeable Mg²⁺content increased significantly by 0.30-1.08 cmol/kg, there is no significance on different parent materials; At 80-100 cm soil layers, soil pH and exchangeable Ca²⁺ contents derived from quaternary red clay, red sandstone and river alluvium parent materials were significantly higher than that of plate shale parent material. Soil exchangeable Al³⁺ content derived from plate shale parent material were significantly higher than that of quaternary red clay parent material, and there were no significant difference between red sandstone and river alluvium. Soil exchangeable Mg²⁺ content derived from quaternary red clay, red sandstone and plate shale parent materials were significantly higher than that of river alluvium parent material. Paddy soil pH derived from different parent materials significantly positively correlated with exchangeable H⁺and Al³⁺, organic matter and total nitrogen, but negatively correlated with exchangeable Ca²⁺and Mg²⁺ (P< 0.01). At 80-100 cm soil layers, the acidity of paddy soil was larger at 0-20 cm soil layer, affected by exchangeable H⁺and Al³⁺, exchangeable Ca²⁺and Mg²⁺, organic matter and total nitrogen, at 80-100 cm soil layers, soil acidity variability was less, affected by parent materials, showing  that acidity of paddy soil derived from red sandstone, river alluvium, and quaternary red clay parent materials was less than that of plate shale.