Cytotoxic bioassay-guided fractionation of methanol extract of Angelicas Sinensis Radix led to the isolation of a new dimeric Z-ligustilide, named neodiligustilide (1), together with three known compounds, Z-ligustilide (2), 11(S),16(R)-dihydroxy-octadeca-9Z,17-dien-12, 14-diyn-1-yl acetate (3), and 3(R),8(S)-falcarindiol (4). Among them, 2 showed the strongest cytotoxicity against L1210 and K562 cell lines with IC$_{50}$ values of 2.27 ${pm}$ 0.10 and 4.78 ${pm}$ 0.18 ${mu}$M, respectively, while 1 showed moderate cytotoxicity wiith IC$_{50}$ values of 5.45 ${pm}$ 0.19 and 9.87 ${pm}$ 0.14 ${mu}$M. Two polyacetylenes, 3 and 4, showed cytotoxicity only against L1210 cell lire with IC$_{50}$ values of 2.60 ${pm}}$ 0.90 and 2.87 ${pm}$ 0.49 ${mu}$M, respectively.