Acid treatments significantly change the physical and chemical properties of red-yellow soil by lowering its pH value and leaching out aluminum (Al) ions that are harmful to the growth of plants. The structure of soil will be damaged, resulting in higher viscosity, higher water retention rate and lower air permeability of the soil. The germination rate of Chinese pine (Pinus tabulacformic Carr.) seeds sowed in soil treated with sulphuric acid (H2SO4) decreased compared to that for untreated soil. The direct cause was the large amount of Al ions leached out because of low pH values (*3.5). The added acid decreased the soil aggregation and increased the number of micro-aggregates (under 250 μin diameter). Such changes increased the soil’s viscosity, which tied the pine needles to the soil after the seeds had germinated and prevented the seedlings from fully developing.