This study describes a new training system based on an unstable platform and a visual interactive system, that was designed to improve postural control ability. The training system consists of an unstable platform, a safety harness, a monitoring device, and a personal computer. To confirm the effects of the training system, a performance test and a training effect test were conducted. The performance test included calibration and the test-retest experiments. The training effect test was conducted on elderly adults. The results of the calibration demonstrated that the average deviations of COP (center of pressure) in all of the other directions were all less than 0.4cm. The results of the test-retest experiment demonstrated that the ICC (intraclass correlation coefficient) of repeatability was reflective of excellent reliability in both the COP maintenance test and the COP movement test. The training reduced the COP sway path by 5% and the average distance of the COP sway by 32.4%. The RMS (root mean square) of COP after training was reduced by 24% and 33% in the ML (medio-lateral) and AP (anterior-posterior) directions. The training also caused a 25% reduction in the results of the Timed Up and Go test. The PTBW (peak torque/body weight) value was increased by 31% and 17.5% in the knee and ankle joints. The experimental results suggest that this postural control training system using an unstable platform could be applied to training to improve postural control ability in elderly adults.