From the rhizomes of Belamcanda chinensis, three new compounds, belalloside A (1), belalloside B (2), and belamphenone (3), along with 13 known compounds, resveratrol (4), iriflophenone (5), irisflorentin (6), tectorigenin (7), irilin D (8), tectoridin (9), iristectorin A (10), iristectorin B (11), hispiduloside, androsin, irigenin, iridin, and jaceoside, have been isolated and characterized. Isolates were evaluated for their cell proliferation stimulatory activity against the MCF-7 and T-47D human breast cancer cell lines. Along with 4, 5, 7, and 9, 3 was shown to stimulate not only MCF-7 but also T-47D human breast cancer cell proliferation.