The insecticidal and repellent activities of essential oil from leaves of Eucalyptus grandis against Culex pipiens quinquefasciatus were investigated. The essential oil was obtained by hydro-distillation and analyzed by gas chromatography-mass spectrometry (GC-MS). The principal constituents in the essential oil were p-cymene (26.794%), α-pinene (15.864%), eucalyptol (6.281%), α-terpineol (4.100%), limonene (3.614%) and borneol (2.519%). The results indicated that the essential oil of Eucalyptus grandis leaves hold insecticidal and repellent activities against Culex pipiens quinquefasciatus. The complete protection time for people against Culex pipiens quinquefasciatus was correlative with its concentration. It could protect people for 7h when its concentration was 50%. Fumigating insecticidal activity was evaluated by airtight fumigation in conical flask. The LC50 values of the essential oil for adults of Culex pipiens quinquefasciatus were 4.5%(0.5h), 3.6%(1h), 2.6%(2h), 2.1%(4h), 0.56%(8h) and 0.56%(24h). The LT50 value of the essential oil was 19.1 min when its concentration was 6.4%.