Objective To determine the resistance levels of Culex pipiens pallens and Cx. pipiens quinquefasciatus from different regions in China to commonly used pyrethroid insecticides and to provide a scientific basis for rational use of chemical insecticides. Methods The filter paper contact method was used to determine the 1 hour knock?down rate and 24 hour mortality of adult mosquitoes exposed to 10 000 mg/L deltamethrin and 10 000 mg/L permethrin. Results The 24 hour mortality of Cx. pipiens pallens and Cx. pipiens quinquefasciatus from three provincial regions in China were all less than 80% when exposed to discriminating doses of deltamethrin and permethrin, so all the mosquito strains were defined as resistant populations. The 24 hour mortality of 7 strains of Cx. pipiens pallens exposed to 10 000 mg/L permethrin were all less than 50%; the 24 hour mortality of 13 strains of mosquitoes exposed to 10 000 mg/L deltamethrin ranged from 1% to 66%, showing different resistance levels. Conclusion Cx. pipiens pallens and Cx. pipiens quinquefasciatus from three provincial regions in China have all developed high resistance to pyrethroid insecticides. The development of insecticide resistance is closely related to the indiscriminated use of pesticides. It is critical to use insecticides appropriately, imperative to monitor the susceptibility, and advisable to develop and apply resistance management tactics.