Bound residue(BR) of 14 C-metsulfuron-methyl (14 C-BR) in seven kinds of soil was significantly negative-related to soil pH and positive-related to the clay content during the initial 20 d of incubation, but only was significantly negative-related to soil pH after 30 d incubation. Again, the soil pH was found to be the dominant factor affecting BR formation from 14 C-metsulfuron-methyl among the basic properties(soil pH, clay, OM and CEC etc.) of soil. The maximum content of 14C-BR in the 7 soils accounted for 19.3% -52.6% of applied amount. In addition, the composition of the 14 C-BR in fluvio marine yellow loamy(S7 ) at the 90 d of incubation was identified using the coupling technique of LC-MS and isotope tracing method. The results showed that the 14 C-[2-amino-4-hydroxyl-6-methyl-1, 3, 5]-triazine, 14 C-[2-amino-4-methoxy-6-methyl-1, 3, 5]-triazine and 14 C-metsulfuron-methyl parent compound constituted the main components of the BR derived from 14 C-metsulfuron-methyl in the S7. The relative percentage of the three compounds accounted for 41.4 %, 35.8 % and 19.3 % of total recovery radioactivity, respectively. The results also indicated that a non- radioactive component, 2-methylformate-benzenesulfonyl-isocyanate, one of the degraded products of metsulfuron-methyl in soil, was also found to be one of the components of the BR. The parent compound in BR can well explain the phytotoxic effect on substitution crops caused by the BR derived from metsulfuron-methyl in soil.