Planar polishing is an important manufacturing process for high-precision planar components. In this study, a real-time dresser and a planar polishing process based on real-time dressing for large-aperture optical plane components were developed. Efficient dressing of a polishing pad surface can be achieved with the real-time dresser. Compared with the conventional method, real-time correction for the surface shape of the polishing pad was realized via the temperature parameter t in the real-time dresser, and this parameter can be optimized through optimization experiments. Finally, a series of experiments was carried out to verify the effectiveness of the real-time dresser on surface dressing. Through the real-time dressing of the polishing pad surface, the flatness peak-valley deviation and the root-mean-square deviation of the flat optical element surface (430×430mm) can reach 3λ and 0.9λ, which is improved by 25% and 33%, respectively.