Abstract: Objective To assess the resistance risk of Culex pipiens pallens to pyriproxyfen in Culex pipiens pallens, to predict the rate of resistance development and to provide the reference for scientific and rational application of insecticides. Methods The resistance strain was developed by group selection, and the realized heritability (h²) of Culex pipiens pallens resistance to deltamethrin was estimated by Tabashnik's method. Results The resistance of Culex pipiens pallens to pyriproxyfen had increased by 5.69-fold after 12 generations of indoor breeding, and the h² of Culex pipiens pallens to pyriproxyfen was 0.02, indicating that a relatively risk of resistance development. Conclusion The results indicate that Culex pipiens pallens has resistance risk to pyriproxyfen, so the application of the insecticide must be scientific and rational.