This work studied the performance improvement of a two-axis solar tracking system by using flat-mirror reflectors. The two- and four-sided flat-mirror reflectors were set on the solar panel with angles of 90°, 120°, and 150° between the panel and flat-mirror reflectors. The highest efficiency, electrical power, and current were observed for four-sided flat mirrors at the angle of 120°, followed by two-sided flat mirrors at the angle of 120°, two-sided flat mirrors at the angle of 150°, two-sided flat mirrors at the angle of 90°, four-sided flat mirrors at the angle of 150°, and four-sided flat mirrors at the angle of 90°, respectively, because when the four-sided flat mirrors were mounted at a suitable degree of 120°, this improved the collected irradiance. At 90°, the four-sided flat mirrors blocked more solar rays than the two-sided ones. At 150°, the angle was too big for the solar ray to be reflected to the solar panel. The results indicated that the performance of the solar tracking system (efficiency, electrical power, and current) was affected by the number and angle of flat mirrors. The results of this study can be applied for the efficient performance of a novel solar tracking system design. This will be beneficial for the use of solar energy.