Two novel 9,11-seco-11-norabietanes, namely taiwanlactones A (1) and B (2), together with 3β-hydroxysugiol (3) and 6α-hydroxysugiol (4), were isolated from the roots of Taiwania cryptomerioides. Their structures were elucidated through spectral studies. The absolute configuration of 1 was elucidated by a modified Mosher’s method. The biotransformation mechanisms of 1 and 2 were proposed.