Abstract: Obtaining high-quality thin films from the active layer is a prerequisite for the preparation of high-performance ternary organic solar cells (TOSCs), introducing the third component with high crystallinity is one of the simple and effective methods to optimize thin films.. A series of TOSCs were prepared using the highly crystalline non-fullerene acceptor ITIC-Th as the third component, together with the non-fullerene acceptor BTP-BO-4F and the polymer donor PM6. As a morphology modifier, ITIC-Th can optimize the molecular arrangement and phase separation of thin films; as a third component with complementary spectral absorption, ITIC-Th can broaden the spectral absorption range of the active layer. In addition, ITIC-Th and BTP-BO-4F easily form an alloy state, which can inhibit the non-radiative recombination of the device. When the content of ITIC-Th is 5%, the TOSCs have the best performance, the power conversion efficiency (PCE) is 17.66%, the short-circuit current density (J_SC) is 26.51 mA·cm⁻², and the open-circuit voltage (V_OC) is 0.862 V , with a fill factor (FF) of 77.32%, which are mainly due to ITIC-Th as the third component that synergistically optimizes the photon trapping, exciton dissociation, carrier transport, and charge collection of the device, resulting in high-performance TOSCs. Selecting a highly crystalline non-fullerene acceptor as the third component is an effective strategy to prepare high-performance TOSCs, which is beneficial to advance the commercialization of TOSCs.