Objective To investigate the changes of plantar pressure distributions in children with the unilateral developmental dysplasia of the hip (DDH) who underwent the Pemberton’s pericapsular osteotomy (PPO) at early age, so as to provide valuable references for clinical therapy and rehabilitation of such patients. Methods Eighteen child patients who underwent PPO before 4 year old were selected as the PPO group, while 18 healthy children at the same age with normal feet were selected as the control group. Footscan system was used to measure the plantar pressure of these subjects during walking. The parameters, i.e. contact area percentage of the total foot contact area (CA%), pressure-time integral (PTI) and contact time percentage of the stance time (CT%) in both PPO group and control group were compared to evaluate changes of the plantar pressures during walking. Results Compared with the sound limb in control group and the unaffected limb in PPO group, the affected limb in PPO group showed higher PTI in the 2nd to 5th toe zone and lower PTI in the medial heel zone. The affected limb in PPO group had a higher CA% in the 4th and 5th metatarsals than the unaffected limb in PPO group and the sound limb in control group, and a lower CA% in the 1st and 2nd metatarsals than the unaffected limb. Compared with the unaffected limb in PPO group and the sound limb in control group, CT% of the affected limb in PPO group increased in the forefoot push-off phase and decreased in the initial contact phase, and the total contact time of the affected limb was shorter than that of the unaffected limb in PPO group and the sound limb in control group. Conclusions There exist residual plantar pressure deviations during walking in DDH patients following PPO at early age, thus a longer period of intensive rehabilitation may be required to change the residual abnormality.