Flavonoids of camphor leaves was extracted by an ionic liquid/aqueous two-phase system in this paper. First, the stability of aqueous two-phase was investigated. Based on single-factor tests, Box-Benhnken center composite experiment was carried out with three factors and three levels of experimental design using extraction time, extraction temperature and pH as the influence factors. Besides, the content of flavonoids was determined by Al(NO3)3-NaNO2-NaOH spectrophotometric method. For a stable ionic liquid aqueous two-phase system, the phase-forming salt is ammonium sulfate ( (NH4)2SO4); the addition amount is 0.8 g; and the volume ratio of the [Bmim] BF4 to water was 2: 2. Response surface analysis showed that for 0.1 g of camphor leaves powder, the influence of factors that affected the extraction rate of flavonoids were in a descending order of extraction time, extraction temperature and pH. The optimized extraction conditions were as follows: extraction time 3.7 h, extraction temperature 82℃, and the solution acidity 9.6. Under the optimum conditions, the extraction rate of flavonoids reached 10.62%. At the same time, the secondary mathematical model for extraction of total flavonoids from camphor leaves with ionic liquid aqueous two-phase system was established, which has a good predictive effect on target product extraction, and provided theoretical guidance for the scale-up experiment or large-scale production of this system.