A cross between bacterial wilt resistant tomato variety "T51A"and susceptible variety 'T9230' was made for mapping bacterial wilt resistance gene(s). Through inoculation test of its F1 and F2 progeny, it was proved that the resistance of 'T51A' to bacterial wilt was controlled by one heterozygous gene and cytoplasm. With 64 EcoR I/Muse I primer combinations, AFLP analysis was performed on two parents and their F2 resistant and susceptible bulks. A total of about 4200 distinguishable bands were amplified, of which two were stable. Genetic linkage analysis of the two polymorphic DNA fragments with the resistance gene(s) was tested in the F2 segregating population derived from the cross between 'T51A' and 'T9230'. The DNA fragment AAG/CAT was found closely linked to one of the bacterial wilt resistant genes, with a genetic distance of 6.7 cM, that was tentatively named RRS-342. The cloned fragment AAG/CAT was sequenced and then successfully converted to a SCAR marker, which can be used more conveniently in marker-assisted selection for tomato resistance to bacterial wilt gene.