Cerebral palsy (CP) is main cause of permanent postural and motor abnormalities due to damage to the immature brain of patients in childhood. Patients with cerebral palsy mostly show abnormal gait postures on the sagittal or frontal plane, such as crouch gait or in-toeing, respectively, so they should learn walking with rehabilitation intervention. In this study, we designed a rehabilitation system using a cable connected to each lower limb of the children with cerebral palsy perpendicular to the sagittal plane to correct abnormal gait posture shown on the frontal plane. The system consisted of an actuator and an inelastic cable, a load cell, and a spring for each leg, and used the fuzzy gain scheduled PID feedback control algorithm to control the cable tension. The designed device used cable-driven mechanism with minimal number of cables and controlled the magnitude and direction of cable tension by tracking knee position of participants. We expect less restriction of voluntary drive of participants with single cable that maintains perpendicular direction to the sagittal plane during gait compared to existing rehabilitation intervention using a cable-driven mechanism. Additional studies will investigate the effectiveness of our designed system to gait posture correction of children with CP who show abnormal gait posture shown on the frontal plane