Abstract: The investigation results showed that the metabolic product I36N from Aspergilius sp. has an obvious inhibition to urease activity of five main kinds of soil in our province. The rate of I36N inhibition on soil urease varied with the activity of soil urease and its effect on higher activity of soil urease is better than its on lower, but was prolonged in the period of retarding urease activity. The inhibiting degree was increased with the increase of I36N application amount and urea concentration used. The pot experiment indicated that I36N could postponed effectively the hydrolysis of urea, delayed high peak of (NH4++NH3)-N from 2 to 4 days and the level of NH3 concentration was lower than control, the change of the pH value was consilience with behaviour of (NH4++NH3)-N in the pot water.