Low molecular weight organic acids（LMWOAs） are a kind of important active matters in soils.The sources and types of LMWOAs,and its environmental effects in soils are reviewed in this paper.The LMWOAs mainly originate from root exudates,decomposition of animal and plant,microbial synthesis and secretion,and the transformation of organic matters.The compositions of organic acids are extremely complicated but can be mainly classified into fatty and aroma families’ organic acids with less than 10 mmol/kg concentrations in soils.The LMWOAs play an important role in soil environmental processes.They could affect the movement,toxicity and bioavailability of heavy metals in soils,and influence the mobilization,transformation and degradation of organic pollutants.The mechanisms of LMWOAs on heavy metals and organic pollutants in soils are different.Some suggestions for further research in this field are proposed.