Objective To assess the risk of deltamethrin resistance development in Musca domestica and predict the rate of resistance development, and to provide a scientific basis for prolonging the service useful life of insecticides, protecting the effectiveness of existing insecticides, maximizing the potential of insecticides, and properly applying insecticides. Methods The resistant M. domestica strain for resistance risk assessment was obtained by lab resistance selection and bioassay. The resistance realized heritability (h₂) was estimated using Tabashnik method, and then the rates of resistance development under different selection pressures were predicted. Results The resistance ratio was increased to 2197.55-fold in the deltamethrin-resistant M. domestica strain after 21 consecutive generations of lab selection. The h₂ of M. domestica to deltamethrin was 0.1571, indicating a relatively high risk of resistance development. According to the general pattern of resistance development in M. domestica (the deltamethrin resistance development in M. domestica can be divided into three stages: the resistance development is very slow within the first seven generations, becomes fast from the 8th generation, and tends to level off in later generations). The h₂ values in three resistance development stages were 0.1016 (F₀-F₇), 0.2140 (F₈-F₁₇), and 0.0250 (F₁₈-F₂₁). According to the h₂ values in different stages, we predicted that 10-fold resistance increase required 7.2-15.9, 4.9-10.8, and 44.4-98.1 generations under different selection pressures (mortality rates: 50%, 60%, 70%, 80%, and 90%). Conclusion The risk of deltamethrin resistance development is relatively high among M. domestica, so attention should be paid to proper use of insecticides based on the situation of targeted pest.