A new furostanol saponin, (25S)-26-O-${eta}$-D-glucopyranosyl-$5{eta}$-furost-20(22)-en-$3{eta}$, $15{eta}$,26-triol-3-O-[${alpha}$-L-rhamnopyranosyl-(1-4)]-${eta}$-D-glucopyranoside, namely, aspacochioside D (1) were isolated from Asparagus cochinchinensis (Lour.) Merr, along with three known saponins, aspacochioside C (2), (25S)-$5{eta}$-spirostan-$3{eta}$-yl-O-[O-${alpha}$-L-rhamnopyranosyl-(1-4)]-${eta}$-D-glucopyranoside (3), and pseudoprotoneodioscin (4). The structure of 1 was elucidated on the basis of chemical reactions and spectral analysis (IR, GC, ESI-MS, $^1H$-NMR, $^{13}C$-NMR, DEPT, HMBC, HMQC and NOESY). The antiproliferative effects of 1-4 were evaluated in a cytotoxicity assay against the human tumor cell line, A549. Compound 2 (Aspacochioside C) exhibited moderate cytotoxicity against A-549, with an $IC_{50}$ value of $3.87{mu}g/mL$.