Abstract: DNA from the mitochondrion(mtDNA) of CMS line BC7-19 and its maintaner of broccoli(Brassica oleracea L.var.italica Plenck.) was extracted by molecular bio-technique,and was marked(using) RAPD reaction.The result showed that the purity of the extracted mtDNA was high by sepharose(electrophoresis).And the result also showed that a special fragment,BMS₁₀₀₀,with about(1000) bp amplificated by primer S66,was peculiar for the mtDNA of male sterile line by RAPD reaction of 40 primers,and the special fragment was initially considered to be relevant to male sterility after sequence analysis.