Soil acidification is an important issue of soil degradation. Agricultural activities play a key role on its acceleration. This review summarized the effects of fertilizers, N cycling, C dynamic and organic matter management on soil acidification. The major reasons leading to acidification of fertilizers are contributed to the large amount of physiological acidic and containing acid, sulfur or chloride fertilizers application. The major processes leading to acidification during N cycling in soils include: 1) the imbalance of cation over anion uptake in the rhizosphere of plants either actively fixing N2 gas or taking up NH4+ ions as the major source of N; 2) the net nitrification of N and the leaching of nitrate with a companion basic cation. The uptake of excess cations over anions by plant results in the acidification of the rhizosphere, and the removal of plant seed and residue which has access cation over anion results in the depletion of base cations and the increase of exchangeable acidity of topsoil. The root respiration and root exudates and bicarbonate leaching should be taken into consideration seriously. The role of plant residues and manures causes soil acidification differing in soil initial pH, and is influenced by the ash alkalinity of plant residues and the saline content of manures as well as the carbon and nitrogen cycling.