Friction Stir Extrusion (FSE) is a modern one step process with high efficiency for conversion and recycling of materials which capable of producing Nano-engineered material via production with good deformability, mechanical and physical properties. Novelty of this production technique is utilization of frictional heat and severe plastic deformation for material flowing, mechanical alloying and finally amendment of powder, chips and other recyclable scraps directly to useful products. Sample’s microstructure was revealed and average grain size was gained for 18 samples. Experimental parameters by use of design of experiments for two factors and analysis of variance were investigated and by the use of experimental results were validated. In this study, the effect of rotational speed in 3 levels and plunge rate in 2 levels were examined on microstructure of produced wires via FSE process. Based on process parameters, there is an equation for grain size prediction was presented by using full factorial design of experiment. Furthermore, normal possibility diagram and residual versus order based on residual theorem were evaluated for systematic error entry and reliability to experimental results. The efficient region on contour diagram reveals that suitable condition of minimum grain size and maximum strength occurred at 250 rpm for rotational speed and 14 mm/min for feed rate. It should be noted that analysis of variance showed that rotational speed, feed rate and interaction of rotational speed and feed rate respectively have a meaningful effect on the grain size of produced wire.