Intermolecular aggregate and regulation of small-molecule acceptors (SMAs) are crucial for photovoltaic performance of organic solar cells (OSCs). In order to investigate the relationships between chemical structures and molecular aggregation, photovoltaic performance, SMA CA2F-M6 based on carbazole with macrocyclic sidechain has been developed. CA2F-BO without macrocyclic sidechain has been synthesized as a comparison. These SMAs have shown similar solubilities in spite of different alkyl sidechains, due to the strong intermolecular aggregation has been suppressed by macrocyclic sidechain. Compared with CA2F-BO, CA2F-M6 exhibits blue-shift absorption in solution, because CA2F-M6 with macrocyclic sidechain shows the larger dihedral angle. CA2F-BO and CA2F-M6 have similar optical bandgap of 1.77 eV, and indicated that they possess similar molecular configuration in thin films. Both of them also show suitable highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy levels with polymer donor PM6. As a result, OSC based on PM6:CA2F-BO exhibit a power conversion efficiency (PCE) of 2.85%. Meanwhile, PM6:CA2F-M6 cell achieves much better PCE of 3.93% with enhanced short-circuit current and fill factor. Further, ternary OSC based on PM6:CA2F-M6:L8-BO has been fabricated and exhibits a promising PCE of 17.61%.