The chemical constituents of Safflower injection were isolated and purified by polyamide, silica gel, Sephadex LH-20, ODS column chromatographies and preparative HPLC. As a result, sixteen compounds have been isolated. Based on the spectral data analysis, their structures were elucidated as scutellarin (1), kaempferol-3-O-β-rutinoside(2), hydroxysafflor yellow A(3), rutin (4), coumalic acid(5), adenosine(6), syringoside(7), (3E)-4-(4'-hydroxyphenyl)-3-buten-2-one(8), (8Z)-decaene-4, 6-diyne-1-Oβ-D-glucopyranoside(9), 4-hydroxybenzaldehyde (10), (2E, 8E) -tetradecadiene-4, 6-diyne-1, 12, 14-triol-1-O-β-D-glucopyranoside (11), kaem-pferol-3-O-β-sophorose (12), uridine (13), roseoside (14), cinnamic acid (15), and kaempferol (16). Compounds 1,2,7,9,11 and 12 were isolated from the Safflower injection for the first time. The anti-platelet aggregation activities of the isolated compounds were assayed. The results indicated all tested compounds exhibited potent activity except for 5, while 2, 3, 9 and 12 showed strong activity against platelet aggregation.