The side-chain has a significant effect on the optical properties and aggregation behaviors of the organic small molecule acceptors, which becomes an important strategy to optimize the photovoltaic performance of organic solar cells (OSCs). In this work, we designed and synthesized three novel nonfused ring electron acceptors (NFREAs) OC4-4Cl-Ph, OC4-4Cl-Th and OC4-4Cl-C8 with hexylbenzene, hexylthiophene and octyl side chains on the π-bridge units. Compared with OC4-4Cl-Ph and OC4-4Cl-Th, OC4-4Cl-C8 with linear alkyl side chain has more red-shift absorption, which is conducive to obtaining higher short-circuit current density. Additionally, the OC4-4Cl-C8 film exhibits a longer exciton diffusion distance and the D18:OC4-4Cl-C8 blend film displays faster hole transfer, weaker bimolecular recombination, and more efficient exciton transport. Furthermore, the D18:OC4-4Cl-C8 blend films can form good nano fibril-like interpenetrating networks, which can facilitate exciton dissociation and charge transport. Finally, OC4-4Cl-C8 based devices can generate an excellent PCE of 16.56%, which is much higher than OC4-4Cl-Ph (12.29%) and OC4-4Cl-Th based (11.00%) ones, being the highest PCE among the NFREA based binary devices. All in all, we have demonstrated that side-chain engineering is an efficient way to achieve high-performance NFREAs.