Objective:This paper is to study the correlation of contents of hesperidin,limonin and nomilin from different parts of citrus with their antioxidant and anti-breast cancer cell activities  Methods:The contents of hesperidin,limonin and nomilin in different parts of citrus,tangerine seed,pith and peel were detected with HPLC method. Furthermore,the in vitro antioxidant effects of the three parts of tangerine were studied with DPPH and FRA  Methods:,and anti-breast cancer cell (MCF-7) activities were studied with MTT assay  Results:The tangerine peel has the highest content of hesperidin,while the tangerine seed contains the highest content of limonoids. Relevant to the content study,tangerine peel has the stronger antioxidant activities in vitro than the other two,while the tangerine seed show more stronger anti-breast cancer cell activities  Conclusion:The antioxidant activites of tangerine seed,pith and peel are mainly correlated with their contents of hesperidin,and the anti-breast cancer cell activities are correlated with their contents of limonins.