Abstract Soil organic matter(SOM) is a kind of natura lorganic matter,extremely complex in composition and important in soil chemistry.Interms of its chemical nature,SOM consists of twoma in portions,that is,humic substances(HS) and non-humic substances.HS is the princ ipal body of SOM,and plays a vital role in soil nutrient recycling and carbon sequestration.SOM attracts numerous scientists for itps importance and complexity.To better understand soil HS and find new research area,this review sums up status quo of the study on form ation-transformation and itps stability(including formation sequences of huminc fractions,inter-transformation,driving factors,isotope discrimination and thermodynamic stability,etc.),chemical composition and structural characteristics(including extraction,purification and structure characterization,etc.) of soil HS and its response to human factors(includ ing the effects of tillage,fertilization and land use,etc.) and puts forth suggestions that further efforts should be made to apply advanced technology to the study,and resume the study of chemical fractionation and structural characteristics of HS and relat ionship between HS formationtransformation and agricultural practices.