【Abstract】 Objective To explore the effect of frozen storage on non-specific esterase (NSE) activity of Culex pipiens pallens and provide a basis for the generalization and application of insecticide-resistance detection of mosquito by biochemical method. Methods The NSE activity of single mosquito was determined based on β-naphthalene acetic acid ester (β-naphthyl acetate, β-NA) as substrate and solid blue B salt (fast blue B salt) as developer. Results The NSE activity of DDVP-resistant strain was obviously higher than that of susceptible strain. For the A value of NSE activity from Cx.pipiens pallens after frozen for 0, 7, 14, 21 and 28 days at -20 ℃, the F value of 4 instar larvae of susceptible strain mosquito was 0.7642 by the complete randomized design variance comparison and the F value of 3-day-old adult female of susceptible strain mosquito was 0.7452. The F value of 4 instar larvae of DDVP resistant strain mosquito was 0.1092, and the F value of 3-day-old adult female of DDVP-resistant strain mosquito was 0.1521. All of the P value were greater than 0.05 and no significant difference was found. Conclusion There was no difference between on the NSE activity of 4 instar larvae and 3-day-old adult female of Cx.pipiens pallens after frozen for 28 days, and mosquitoes collected from the field could be taken to the lab for batch determination.