According to the principle of foot biomechanics, a three-division method of measuring distributed force of the sole was proposed, and the corresponding distributed force measuring platform (DFP) system was developed. Twenty-seven young adults and forty elder adults were randomly selected for stability measurements in the continuous process from double-leg stance with eyes closed to double-leg stance with eyes opened and to single-leg stance with eyes opened. The foot support principle was analyzed by solving the CoP trajectories (95% confidence circle area) of three zones of the right foot and the CoP trajectories offset in three standing stages. The maximum values of the CoP trajectory range in the three partitions of the youth and elderly groups were respectively 27. 00~227. 46 mm 2 and 116. 35~387. 22 mm 2 , the maximum offsets of the anterior-posterior direction were 6. 07±3. 13 mm and 5. 88±3. 21 mm respectively, and the maximum offsets of the medial-lateral direction were 6. 51±2. 29 mm and 6. 77±2. 34 mm respectively. The results show that the CoP trajectories are concentrated on the bottom end of the calcaneus and the medial and lateral end points of the transverse arch of the metatarsophalangeal joint in both doubleleg stance and single-leg stance, and the position is less affected by the difference in postural stability.