Objective To compare the differences in gait characteristics and stability of women walking with or without sports bra. Methods Twelve women with C cup breast were required to walk on the treadmill (at the speed of 6 km/h) with and without sports bras, respectively. Their gait parameters were collected by using Qualisys Track Manager high-speed infrared motion capture system. Results Compared with the bare-breasted condition, the maximum and minimum angles of the upper trunk were significantly smaller when subjects wearing the sports bra, the range of trunk flexion angles and trunk torsion angles were also relatively smaller, and the standard deviation of hip flexion angles during 10 gait cycles was obviously smaller. However, no differences were found in stride frequency between two breast support conditions. Conclusions Different breast support conditions have a significant influence on the upper trunk angle, trunk flexion angle and trunk torsion angle. Walking without bra will increase the range of trunk angle and deteriorate the walking stability. The stride frequencies under different breast support conditions have individual differences.