Processing parameters of micro thixoforming, such as height-diameter ratio, die/punch temperature, billet temperature, and punch speed, have direct and complex impact on final quality of the workpiece, which is to be applied as the reaction plate of a microreactor for hydrogen production from methanol steam reforming. The micro/meso features of the workpiece, which is for catalyst loading, are micro-pin-fin arrays. Size of the surface area and uniformity of the pin-fins are quantified by average height (Ha) and relative standard deviation (RSD). An orthogonal experiment design is adopted to investigate the influence of the parameters on the semi-solid forming process. The results of the orthogonal experiment show that the optimum parameters are 150 °C for die/punch temperature, 576 °C for billet temperature, 0.14 for height-diameter ratio and 8.33 mm/s for punch speed. The experimental results validate that the optimized processing parameters can improve the quality of the reaction plate with micro-pin-fin arrays.