Chemical investigation of the basic fraction from the roots of Spiraea japonica var. acuta has resulted in the isolation of three new diterpene alkaloids, spiramines X (1), Y (2) and Z (3), along with five known compounds, spiradine F (4), and spiramines A, B, P (5), and U (6). The structures of 1-3 were determined by spectral and chemical methods. Antiplatelet aggregation activities of compounds (1- 6) were tested.