The present invention discloses a breeding method and application of a new downy mildew-resistant interspecific hybrid Cucumis sativus variety. The breeding method comprises the following steps: performing hybridization to obtain F1 with the high-generation inbred line CCMC of ‘；Changchun dense thorn Cucumis sativus’； as a female parent and a Cucumis sativus-Cucumis hystrix introgression line material IL52 as a male parent, selfing the hybrid F1 to obtain F2, and continuously constructing an F6 recombinant inbred line by the single seed transfer method； and by identifying of phenotypes of the recombinant inbred line populations during the natural inoculation of downy mildew at the adult plant stage in the field for 4 years, recombinant individuals with high resistance and good fruit marketability will be screened； and utilizing backcrossing and molecular marker-assisted selection to obtain the individuals as the new downy mildew-resistant interspecific hybrid Cucumis sativus variety in which the genotype in the dm5.2 region coincides with the banding pattern of IL52 and the other chromosome regions are the banding pattern of ‘；Changchun dense thorn Cucumis sativus’；. The new variety has a high downy mildew-resistant trait, high yield and excellent fruit quality.
