Abstract: The number of nitrosobacteria, nitrobacteria, pH and nitrifying capacity of soil were determined in 4-10 weeks after application of Metalaxyl. The result showed that the nitrification of soil was inhibited by Metalaxyl in a certain degree. It was appeared that Metalaxyl had inhibition on nitrifying capacity with 25 mg a. i/kg soil in 4-8 weeks after the bactericide used.