Laboratory study on dynamics and forms of ¹⁴C-metsulfuron-methyl residual was investigated in 15 soils.It was found that there was a steady loss of ¹⁴C-metsulfuron-methyl with time in soils,which could be described by the firs-torder equation.Soil pH was positively related to the half-life,total ¹⁴C-residues and extractable ¹⁴C-residues,but negatively to the bound ¹⁴C-residues.The degradation rates and ¹⁴C-residues binding rate varied with the soil microbial biomass.The humic substances and clay could also influence the degradation rates and residual forms of ¹⁴C-metsulfuronmethyl in soils.Soil pH,microbial biomass and fulvic acid were the most significant factors controlling the degradation rates and forms of ¹⁴C-metsulfuron-methyl residual in soils.The regression equations between metsulfuron-methyl residues and soil propert ies were established after the stepwise regression analysis.