Abstract: Wheat Rhizoctonia cerealis were treated by triadimenol, tebuconazole, and 2% triadimenol-tebuconazole seed coating formulation(1.2% triadimenol and 0.8% tebuconazole), respectively. Its ergosterol was extracted by the saponification method, then measured by HPLC. The results showed that seven days after the wheat Rhizoctonia cerealis treated by three chemicals on the concentration of 5.0 μg/mL, the inhibition rates of the three chemicals were 60.4％, 63.8％ and 63.8%, respectively. With the increase of the concentrations, the content of ergosterol decreased, which indicated that the inhibition effect of chemicals became stronger. When the concentration of the three chemicals were in the same level, the content of ergosterol treated by triadimenol was the highest, followed by tebuconazole and triadimenol-tebuconazole seed coating formulation. It was concluded that the three chemicals could inhibit the biosynthesis of ergosterol in wheat Rhizoctonia cerealis , so its content reduced remarkably.