Abstract: In order to clarify the synergistic effects of mixed JS399-19 and Hexaconazole to Rhizoctonia cerealis and R. solani and to find the best mixed ratio of two preparations, the JS399-19 and Hexaconazole and their mixtures-made up by mixing the two pesticides in five different ratios, on Rhizoctonia cerealis and R. solani were tested by mycelial growth rate method. Experimental results demonstrated that EC50 of JS399-19, Hexaconazole, and their five different ratios to Rhizoctonia cerealis were 0.212, 0.339, 0.227, 0.207, 0.213, 0.315, 0.320 mg/L. The efficiency coefficients of the five different ratios to Rhizoctonia cerealis were 1.35, 1.52, 1.51, 1.02, 1.02. Experimental results demonstrated that EC50 of JS399-19, Hexaconazole, and their five different ratios to R. solani were 0.452, 2.984, 1.091, 1.139, 1.217, 1.280, 1.781 mg/L. The efficiency coefficients of the five different ratios to R. solani were 1.41, 1.54, 1.57, 1.59, 1.20. The mixed ratio of two preparation 1:(7-9) to Rhizoctonia cerealis and R. solani had synergistic effects.