Abstract: In the past two decades, solution-processed bulk heterojunction organic solar cells (BHJ-OSCs) have developed rapidly, and their power conversion efficiency (PCE) has exceeded 19%, but the relatively large energy loss (E_loss) of the devices has become a bottleneck factor limiting their photovoltaic performance. Therefore, further improving the PCE of OSCs by reducing the energy loss has become the focus of research in this field. By analyzing the photophysical processes in OSCs, the mechanisms of different energy loss pathways are discussed, and the following four strategies are reviewed: (1) reducing the energy offset between donors and acceptors, (2) reducing the energy disorder, (3) improving the luminescence efficiency of the devices, and (4) reducing the reorganization energy. This paper systematically summarizes the recent progress in reducing the E_loss of non-fullerene OSCs systems, which provides an important reference for further improvement of the performance of such devices.