Abstract: The fumigation activity and synergistic effects of certain mixtures of steam-distilled essential oils from Cinnamomum camphora leaves, Cinnamomum camphora fruits and Cinnamomum pedunculatum leaves against Culex pipiens quinquefasciatus was evaluated. The results showed that the fumigation 24 h LC50 values of essential oil from C. camphora leaves, C. camphora fruits and C. pedunculatum leaves against adults of C. pipiens quinquefasciatus were 7.47, 4.92 and 5.70 μg/cm3, respectively. At the given dosage of fumigation, the KT50 values (the time to knock down 50% of the mosquito population) were 16.62, 15.91 and 16.98 min, respectively, when the fumigation time was 20 min. The co-toxicity coefficient of C. camphora leaves oil and C. pedunculatum leaves oil mixed at a volume ratio of 1:9, 3:7 and 5:5 against mosquito adults were 152.09, 158.20 and 152.86, respectively. The co-toxicity coefficient of C. camphora fruits oil and C. pedunculatum leaves oil mixed at a volume ratio of 1:9, 5:5 and 7:3 against mosquito adults were 145.73, 146.30 and 139.79, respectively. The results showed that the three essential oils possessed high fumigation activity against C. pipiens quinquefasciatus, and the certain ratio mixtures of the oils revealed remarkable synergistic effect of fumigation against C. pipiens quinquefasciatus.