Objective To obtain kinematic and kinetic parameters of the ankle joint from young man with ankle lateral collateral ligament (LCL) injury during walking, and to investigate the biomechanical characteristics of gaits by these ankle-injured patients. Methods Qualysis MCU500 3D image capture system and Kistler 3D force platform were used to test synchronously the gait of 15 patients with LCL injury and 15 healthy young men. Results For patients with LCL injury, the vertical component of ground reaction force (GRF) changed smoothly, and the posterior anterior component of GRF and the medial-lateral component of GRF were larger than that of healthy young men during anterior-middle support phase and during 60% anterior support phase, respectively. The moment of ankle joint plantar flexion in patients with LCL injury and in healthy young men was similar. The largest ecstrophy and extorsion moment of the ankle joint was found at the injured side of patients with LCL injury, with the largest output power in the sound limb of them. Conclusions The stability of the ankle joint in patient with LCL injury was decreased, with abnormal gait appeared during walking. The sound limb had to compensate the injured limb to reduce the load on the injured limb by switching quickly to the phase of vertical support at the moment of heel-striking. This study provides theoretical references for both the prevention and treatment of ankle joint injury in clinic and rehabilitation training.