[Objectives]  To clarify the inheritance of resistance to deltamethrin in Neoseiulus barkeri and provide theoretical guidance for the improved control of field pests. [Methods]  A deltamethrin resistant strain of N. barkeri was created by the direct spraying of deltamethrin, and the degree of dominance (D), cytoplasmic factors and genes involved in resistance were determined by crossing and backcrossing resistant (RR) and susceptible (SS) strains. [Results]  After 30 generations of selection, a resistant strain (RR) with 226.38-fold higher tolerance for deltamethrin than the sensitive strain, was obtained. D values for the F₁ (SS♀×RR♂ and RR♀×SS♂) were in the range 0<D<1 (0.893 8 and 0.761 7, respectively), indicating incomplete dominance. The 95% confidence limits of these two D values overlap, indicating that there is no significant difference between the D_SR and D_RS strains. This demonstrates that the gene conferring deltamethrin resistance is mainly on the autosome. A Chi-square (c²) goodness-of-fit test indicates that the mortality levels of F₂ females (BC_1SR and BC_1RS) were significantly different (c²=15.51, df=8, P˂0.05) from those expected under the assumption of multiple gene control. [Conclusion]  The inheritance of resistance to deltamethrin in N. barkeri allows resistance to develop rapidly. Release of the resistant strain should reduce the conflict between biological and chemical control.