In the past few decades, polymer solar cells (PSCs) have gained great progress. And fullerene PSCs occupy a dominant position in the early stage of the development of PSCs. Recently, non-fullerene PSCs have gained more attention because of their advantages, such as good absorption in the visible and near infra-red (NIR) region, high tunability of energy levels, better complementary absorption spectra with donors. Thus, numerous efforts have focused on the synthesis and modulation of small molecular acceptor (SMAs). And lots of non-fullerene PSCs have achieved higher power conversion efficiencies than fullerene PSCs. This short review focuses on the progress of non-fullerene small-molecule acceptors for high efficiency PSCs in recent years. And it would provide new ideas for designing high efficiency PSCs.