Abstract: Nine new title compounds, 2-(1,5-pentamethylene)-5-substituted imino-Δ3-1,3,4-thiadiazoline were synthesized from cyclohexanone via N-substituted cyclohexanone thiosemicarbazones,followed by oxidative cyclisation on treatment with manganese dioxide. The structure of all the compounds were confirmed by IR,13C NMR and elemental analysis. Preliminary bioassays showed that all the compounds had some fungicidal activity to Rhizoctonia solani Kühn and Veticillium dahlide at the concentration of 100 mg/L and 50 mg/L. The inhibition rate to R.solani reached 90% for five compounds at the concentration of 50 mg/L.