Objective To investigate the relationship between Wolbachia and deltamethrin resistance in Culex pipiens pal?lens. Methods PCR was used to detect Wolbachia in Culex pipiens pallens and qRT?PCR was performed to determine and compare the expression of Wolbachia between deltamethrin?resistant and ?susceptible strains of Culex pipiens pallens. Re?sults Wolbachia was detected in Culex pipiens pallens in the laboratory. The expression of Wolbachia was 18.42 3.69 4.43 3.96 6.31 1.55 and 3.76 folds higher in the deltamethrin?resistant strain than in susceptible strain in the egg 1st 2nd 3rd 4th stages, and male and female adults, but there was no statistical difference in the pupae stage. The expression of Wolbachia was 2.64 folds higher in deltamethrin?resistant females than in susceptible females which were caught in Jiangxinzhou of Nan?jing. Conclusion Wolbachia is associated with deltamethrin resistance in Culex pipines pallens.