A new acridone alkaloid, 5-hydroxynoracronycine alcohol (4), along with six known acridone alkaloids, glycocitrine-I (1), 5-hydroxynoracronycine (2), citrusinine-I (3), grandisine-I (5), natsucitrine-II (6), and citracridone-III (7), were isolated from the stem bark of Citrus maxima f. buntan. Their structures were established on the basis of spectroscopic methods (1H NMR, 13C NMR, and 2D NMR) and comparison with literature data. Compounds 1-4 and 7 were tested for cytotoxicity in vitro on HepG2, KB, H2058, COLO 201, HA22T, and Chang liver cell lines. These five alkaloids showed cytotoxic effects (IC50 < 50 μM) on HepG2 and KB cell lines, while they did not exhibit cytotoxic activity (IC50 > 100 μM) on H2058, COLO 201, HA22T, and Chang liver cell lines. Among these alkaloids, compound 4 was most cytotoxic to the KB epidermoid carcinoma cell line (IC50 = 19.5 μM), and compound 7 was most cytotoxic to HepG2 hepatoma cell line (IC50 = 17.0 μM).