Background: Children with Down syndrome frequently show postponed beginning of independent walking. Treadmill preparing is a compelling intercession that invigorate a prior walking start. In addition, orthosis regularly are given to children with Down syndrome to increase steadiness and advance prior free walking. The purpose of this study was to give knowledge into the formative results of early orthosis use in a mix with treadmill training in children with Down syndrome contrasted with treadmill training alone. Methods: Thirty patients in with Down syndrome (age ranges from 7 to 11) years were equally divided into two groups; control group (A) and study group (B). The control group received designated physical therapy program to facilitate balance during walking for one hour, while the study group receiving treadmill exercise with supramalleolar orthosis for twenty-five minutes in addition to the same program which given to the control group for thirty-five minutes were used for treatment in the out-patient clinic of the Faculty of Physical Therapy, Cairo University. Results: The results uncovered a measurably critical improvement in the measuring variables of both groups when contrasting their pre and post treatment mean values. Comparing the two groups' post –treatment variables, significant difference is revealed in favor of the study group. Conclusion: The obtained results strongly support the introduction of treadmill exercise with supramalleolar orthosis as an additional procedure to the treatment program of Down syndrome children.