Abstract: 【Objective】 To establish an evaluation system based on the time-dose-mortality （TDM） model for dissec-ting the variety-specific pathogenicity of Bombyx mori bidensovirus （BmBDV）， thereby providing a precise quantitative tool for silkworm disease-resistant breeding. 【Method】 Fourth-instar larvae of silkworm breeds Jingsong×Haoyue and 9 Fu were used as experimental subjects. BmBDV was inoculated via artificial diet feeding， and pathological characteristics following infection were observed. Larvae were exposed to a gradient of viral concentrations ranging from 1×10⁵ to 1×10⁹ ng/μL， and mortality was recorded at designated time points. The TDM model was applied to dynamically fit the mortality data， enabling calculation of the median lethal concentration （LD₅₀） at different post-inoculation time points and the median lethal time （LT₅₀） at specific viral doses. Model fitting effect was assessed using Hosmer-Lemeshow test. 【Result】 Following BmBDV inoculation in 4^th instar larvae of both 9 Fu and Jingsong×Haoyue， disease symptoms first appeared on the 5^th d of the 5^th instar， with overt clinical signs manifesting by the 9^th d of the 5^th instar. Infected larvae ultimately died from digestive dysfunction and malnutrition； cadavers were desiccated and shrunken， with no milky exudate characteristic of nuclear polyhedrosis or flacherie. Great body weight divergence was observed from the onset of the 5^th instar， with larvae in higher-concentration groups exhibiting lower silkworm body weight. Under identical inoculation schedules， silkworm mortality rate increased monotonically with BmBDV concentration. Jingsong×Haoyue was identified as a susceptible strain， reaching 100% mortality rate by the 2^nd d of the 5^th instar， whereas 9 Fu demonstrated markedly stronger resistance， with mortality rate of only 66% at the same time point， which was obviously lower than Jingsong×Haoyue. TDM model fitting revealed that the cumulative time-effect parameters of Jingsong×Haoyue and 9 Fu increased progressively over time， though the rate of increase attenuated in later stages. Both dose-effect and time-effect parameters reached extremely significant level in t test （P<0.01）， and the standard errors of dose-effect slope estimates were significantly lower than the estimated values （P<0.05）. Model predictions indicated that peak mortality in both Jingsong×Haoyue and 9 Fu occurred on the 10^th d post-inoculation. As inoculation time extended， the viral concentration required to achieve effective infection declined， with corresponding reductions in both LD₅₀ and 90% lethal concentration （LD₉₀）， demonstrating a progressive enhancement of the dose-response effect over time. 【Conclusion】 Resistance to BmBDV in silkworm is breed-specific. 9 Fu exhibits supra-threshold resistance， a phenotype potentially associated with the developmental timing of integument maturation and suppression of viral replication. The TDM model successfully quantifies the dose-time interaction of BmBDV infection， capturing the temporal decline in LD₅₀ and the dose-dependent reduction in LT₅₀. A viral DNA concentration of 1×10⁵ ng/μL is recommended as the optimal inoculation dose， balancing disease control efficacy with preservation of economic traits， providing a precise operational window for disease-resistant breeding programs and field-level virus management.