Abstract: The effects of iodosulfuron-methyl sodium on several biological indicators in soil were studied by stimulated methods in laboratory. The results showed that the soil urease activity and microbial biomass carbon were restrained significantly, and then, come consistent with CK, and the catalase activity of soil was lightly restrained at first, then stimulated and recovered as the soil treated with iodosulfuron-methyl sodium at a level of 1 mg/kg. Iodosulfuron-methyl sodium also had some effects on soil respiration, the higher concentration the greater influence during the early days. But as time goes on, the restraining of respiration turns to stimulating, and after 12 days it showed almost no difference between the respiration of soil treated by iodosulfuron-methyl sodium and CK soil. The result of statistical analysis showed that iodosulfuron-methyl sodium is a low toxicity or not harmful herbicide.