A　novel　fluorescence　method　has　been　established　for　the　determination　of　gene　fragment　and　PCR　amplification　products　related　to　chronic　myelogenous　leukemia　(CML).　A　molecular　beacon　(MB)　which　comprises　a　DNA　loop　section,　a　pair　of　fluorophore　(tetramethoxyl　rhodamine,　TAMRA),　and　a　quencher　(4-(2-methyl-on-amino-azobenzene)　benzoate,　DABCYL)　was　designed.　The　loop　sequence　of　MB　was　designed　according　to　the　DNA　sequence　relating　to　CML　(type　b3a2)　which　contained　a　single-stranded　oligonucleotide.　Before　hybridization,　the　fluorescence　from　the　TAMRA　had　been　quenched　by　the　DABCYL.　After　hybridization　with　the　complementary　DNA,　the　quencher　will　become　far　away　from　the　TAMRA,　and　the　fluorescence　intensity　detected　will　increase.　Changes　in　the　fluorescence　intensity　have　a　linear　relationship　with　the　concentration　of　complementary　DNA　(C)　in　the　range　of　4.0　x　10(-9)-3.2　x　10(-8)　mol/L,　with　a　correlation　coefficient　of　0.9973;　the　detection　limit　was　6.0　x　10(-10)　mol/L　(S/N　=　3).　The　developed　method　has　high　selectivity,　which　can　be　used　to　discriminate　single-base　mismatch　sequence.　The　method　has　been　applied　to　detect　the　short-stranded　CML　DNA　fragment　(278　bp)　with　high　sensitivity.　This　approach　is　a　promising　method　for　the　detection　of　CML　in　real　samples　for　medical　diagnostics.