In this study, the structure and mechanical properties of micro-fibrillated cellulose fiber -reinforced polyethylene (CeFRP) products prepared via melt processing were investigated. The CeFRP was prepared through the Reactive micro-Fibrillation Extrusion (RFE) Process in which high density polyethylene (HDPE) mixed with wood pulp was kneaded and compounded using a twin-screw extruder to nano-fibrillate and nano-disperse the wood pulp. WAXD measurement of the injection molded products revealed that molecular orientation of the HDPE in the core part was improved while that in the skin part was suppressed for CeFRP, which influenced the mechanical properties. Structural analyses also revealed that the orientation distribution of cellulose was homogeneous throughout the thickness of composite.