Objective To study the chemical constituents of whole plant of Phyllanthus urinaria and their biological activity. Methods The chemical constituents were isolated and purified by repeated column chromatography over silica gel, Rp-C-18 (reverse phase), MCI, and Sephadex LH-20, as well as semi-preparative HPLC. NMR spectroscopic analyses were used for the structure identification. In this case, the inhibitory rate of NO production of the isolated triterpenoids was evaluated. Results Seven triterpenoids, identified as 28-norlup-20(29)-ene-3,17 beta-diol (1), betulin (2), beta-betulinic acid (3), 3-oxofriedelan-28-oic acid (4), oleanolic acid (5), 3R-E - coumaroyltaraxerol (6), and 3R-Z-coumaroyltaraxerol (7), were isolated and identified from the whole plants of P. urinaria. Compounds 1-5 exerted inhibitory effects against NO production in LPS-induced RAW 264.7 mouse macrophages with the inhibitory rate of NO production ranging from 4.0% to 27.8% at the concentration of 25 mu mol/L. Conclusion To the best of our knowledge, this is the first report of compounds 1-4, 6, and 7 from the family Euphorbiaceae. Compounds 1-5 exhibited inhibitory effects against NO production in LPS-induced RAW 264.7 mouse macrophages.