Molecular identification on diploid and tetraploid watermelon breeding lines which were resistant to Fusarium wilt was carried out with the published dCAPS marker "4451_fon" which was closely linked with resistance gene of Fusarium wilt race 1. The results showed that all the diploid and tetraploid lines expressed as re- sistant genotype, which were defined as Fusarium wilt-resistant materials. The re- sults were consistent with that of artificial inoculation identification. Molecular identifi- cation results also indicated that the resistant lines were homozygote, and the Fusarium wilt-resistant gene would not separate or lose during the future self- crossed purification. Therefore, resistance selection would not be necessary in their progeny populations. The study results thought that dCAPS marker "4451_fon" could be applied on molecular marker assisted selection for Fusarium wilt resistance breeding in watermelon to increase breeding selection efficiency and accelerate breeding progress.