Objective To analyze the symmetry characteristics of gait dynamics, kinematics and spatial and temporal parameters in children with mild Leg Length Discrepancy (LLD), and to explore the possible influence or risk of LLD on children"s growth, so as to provide theoretical basis for early assessment and intervention. Methods Using a modified traditional three-dimensional model, 29 markers were placed on the body surface of each subject to collect gait parameters and calculate the symmetry index (SI). The spatial distance of the ipsilateral markers between anterior superior iliac spine and the external ankle in the standing position was recorded as the length of the legs, and children with more than 0.5 cm and less than 2.5 cm leg length difference were included in the group of 59 cases with mild LLD, and those with less than 0.5cm leg length difference were included in the group of 42 cases as the control group, and then divided into the groups of 1-6 and 7-14 years of age according to the ages of the children and were statistically analyzed separately, and the symmetry index difference of the gait parameters was calculated between groups. Results The SI of the vertical ground reaction force and the maximum power of the knee joint were significantly different between children with mild LLD and normal children aged 1-6. The SI of the pelvis motion were significantly different between children with mild LLD and normal children aged 7-14. Conclusions The imbalance in muscle strength and control of the unequal leg length in children in the younger age groups, and the imbalance at the pelvic motion appears as the gait pattern matures, suggests clinical attention or early assessment.