From the ethyl acetate fraction of the stem bark of Camellia japonica, three new triterpenoids, 3β-O-acetyl-16β-hydroxy-12-oxoolean (6), 3β-O-acetyl-16β-hydroxy-11-oxoolean-12-ene (7), and 3β-O-acetyl-16β-hydroxyolean-12-ene (8), along with seven known compounds, 3α-hydroxy-1-oxofriedelan (1), friedelin (2), 3β-friedelanol (3), canophyllol (4), 3-oxofriedelan-1(2)-ene (5), β-amyrin (9), camellenodiol (10), and camelledionol (11) were isolated. Their structures were established on the basis of spectroscopic analysis and chemical evidence. The isolated compounds were tested in vitro for their cytotoxic activities against the A549, LLC, HL-60 and MCF-7 cancer cell lines. Among them, compound 8 showed cytotoxicity against LLC and HL-60 cancer cell lines with IC₅₀ values of 25.2 and 21.7 μM, respectively.