The purpose of this research is to investigate the impact of movable solar shading on energy performance in subtropical regions of China. An office building retrofitted with a novel internal roller shading system consisting of two shading layers was selected to carry out field measurements and numerous computer simulations were conducted in order to quantify the energy saving performance of this solar shading system, which was further compared with commonly used Low-E windows and regular fabric roller shades. The results show that the solar transmittance ratio is only 1.3% to 7% depending on used solar shading layers in summer and there is almost no negative impact on heating season in winter. The room base temperature reduction ranges from 4–14°C in summer, indicating a significant indoor thermal performance improvement. Meanwhile, the total energy saving for this shading system is 26.06%, 24.42% and over 50%, respectively, compared to Low-E windows, fabric roller shades and the bare window case. Thus, this novel solar shading system is a high energy saving measure and can be widely used in a subtropical zone.