[Purpose] The purpose of this study was to investigate the changes of the center of pressure (COP) trace in fall-prone older adults during obstacle crossing before and after Tai Chi exercise. [Subjects] Fifty-two fall-prone older adults participated in either a 12-week intervention of Tai Chi exercise or in a health education program. [Methods] The subjects were pre- and post-tested in a task in which they were asked to step over an obstacle from a quiet stance. The subjects were divided into two groups (the experimental group and the control group). Participants in the experimental group received Tai Chi exercise emphasizing dynamic weight shifting three times weekly. Participants in the control group met for one-hour weekly and listened to lectures about health promotion. Performance was assessed by recording the changes in the displacement of the COP in the anteroposterior (A-P) and mediolateral (M-L) directions using a force platform. [Results] The experimental group of subjects significantly increased A-P and M-L displacement of the COP after Tai Chi exercise (p<0.05). [Conclusion] This study shows that participation in Tai Chi exercise increased the magnitude of the A-P and M-L displacement of the COP, thereby improving the ability of older adults to generate momentum to initiate gait.