This paper presents two main parts: The first part involves manufacturing the specimens form composite material for mechanical testing (tensile, flexural and fatigue tests), then design a custom foot orthesis (CFO) and manufacturing from composite lamination (3nylglass 2carbon fiber 3nylglass) for patient suffer from flexible flat foot since birth and over-pronation. The second part of this research involves a design a model of custom foot orthesis in (solid work 2018) and then analysis of custom foot orthosis in engineering analysis program (ANSYS V.18.2).The applied pressure in boundary condition adopted from Force Sensor Resistance (FSR 402 ) in various regions in foot after wearing composite CFO. Used a composite materials in engineering data, then calculated von- Misses, safety factor of fatigue and total deformation .The results showed that the ultimate stress (Ϭult) and the fatigue limit for lamination1 (3nylglass+2fiberglass+3nylglass) is (46.017) MPa and (27 MPa) respectively, and the ultimate stress (Ϭult) and the fatigue limit increase for lamination2 (3nylglass+2carbon fiber+3nylglass) to (101.282) MPa and (40 MPa( respectively. The results of engineering analysis in lamination 2 (NCN) show the safety factor,the maximum total deformation, the von-Misses stress are (11.889) , (0.19 mm)and (6.98 MPa) respectively, the CFO is very safe in design.