From ethyl acetate extracts of the ethanol extract Citrus Hystrix collected in Champasack, South Laos,we described here the isolation and structure elucidation of two compounds flavonoids: quercetin(KS1), myricetin (KS2). According to the research results show both compound exhibits a wide rangeof activities that include strong anti-oxidant, anticancer, antidiabetic and anti-inflammatory activities.Key words: Citrus Hystrix, flavonoids, quercetin, myricetin, anti-oxidant.