Ternary blend has been an effective strategy for achieving high efficiency in organic solar cells (OSCs). Herein, a non-fullerene small molecule acceptor (C8-DTC) was synthesized and added to the PM6: Y6 system as a third component. By adding 10% of C8-DTC as the second acceptor in the PM6:Y6 system, an impressive power conversion efficiency of 17.52% was achieved with simultaneously increased open-circuit voltage, short-circuit current-density, and fill factor. The reduced voltage loss was due to the lowered non-radiative recombination loss in comparison with the binary device. It was also found that a small amount of C8-DTC in the PM6:Y6 blend resulted in enhanced charge separation and charge transport by providing possible extra channels of hole extraction. And the ternary system formed a good phase separation and favored bi-continuous transport network, which is more conducive to balance the electron and hole transport. The results indicate that the ternary system formed by C8-DTC as the third component is an effective method to improve the performance of the PM6:Y6 based OSCs.