Abstract: Nineteen 6,7-(methlenedioxy)benzothiopyran-4-one derivatives were synthesized from 1,3-benzodioxole by bromination,sulfuration and cyclization.Their structures were confirmed by 1H NMR and MS.The preliminary bioassay showed that all of the synthesized compounds have different inhibition on seven tested plant pathogenic fungi at the concentration of 50 mg/L.The inhibition rates of compound 5b,5i,5k and 5l against Fusarium solani reached up to 75% and that of compounds 5h and 5i were 67.7% and 70.4% against Botrytis cinerea,respectively.