Researches on low-molecular-weight or minor organic acids in soil are reviewed in this paper. Minor organic acids in soil are results of decomposition of animal and plant residues, root exudation and microbial synthesis. Their compositions are very complicated, but can be sorted mainly into fatty group and aroma group. Their concentrations ranged from μmol to mmol. Minor organic acids play an important role in soil processes, accelerating mineral dissolution, promoting pedogenic processes, acidifying rhizospheric soil, influencing activities of soil microbes and enzymes, stimulating nutrient transformation in the rhizosphere, enhancing plant absorption and utilization of nutrition such as P, Fe, alleviating aluminium poisoning on plants and affecting movement and plant absorption of heavy metals in soil. Besides, minor organic acids have dominant functions in allelopathy. At the end of the paper, the author has brought forward some suggestions for further research in this field.