Chemical constituents were isolated and purified from the water extract of Artemisia annua by column chromatography of HP-20 macroporous resin, silica gel, ODS, Sephadex LH-20, HW-40, and semi-preparative RP-HPLC. Their structures were elucidated by physicochemical properties and spectral analyses. As a result, Fifteen compounds were isolated and identified as vitexnegheteroin M(1), sibricose A5(2), securoside A(3), citrusin D(4), annphenone(5), E-melilotoside(6), esculetin(7), scopoletin-7-O-β-D-glucoside(8), eleutheroside B_1(9), chrysosplenol D(10), patuletin-3-O-β-D-glucopyranoside(11), quercetin-7-O-β-D-glucoside(12), rutin(13), apigenin 6,8-di-C-β-D-glucopyranoside(14), isoschaftoside(15), among them, compounds 1-4 were identified from Artemisia for the first time. Additionally, the isolates were evaluated for their inhibitory effects on the production of PGE_2 in LPS-simulated RAW264.7 macrophages. The results showed that compounds 1, 2, 8, and 10-15 could reduce PGE_2 levels, to a certain extent.