Organic lead trihalide perovskite materials have attracted considerable interest for their successful application as light absorbers in efficient photovoltaic cells. Several lead sources have been used for thepreparation of perovskites, among which lead acetate (Pb(Ac)2) is an important candidate. However, simply mixing Pb(Ac)2 and methylamine iodide in N,N-dimethylformamide solvent leads to poor perovskite morphology, which is disadvantageous for the device performance. Herein, we used dimethyl sulfoxide (DMSO) as a solvent additive to improve the quality of Pb(Ac)2-based perovskite films. We observed that using 5.0% DMSO could significantly enhance the crystallinity of the perovskite film with enlarged domain size. Consequently, the power conversion efficiency (PCE) of the relevant perovskite Solar cells (PSCs) was drastically enhanced from 12.88 to 16.59% (on average), with simultaneous improvement in the open-circuit voltage, short-circuit current density, and fill factor. A champion PCE of 17.06% with negligible hysteresis was achieved for PSCs prepared using 5.0% DMSO as the solvent additive. Our results indicate that using DMSO for the preparation of a Pb(Ac)2-based perovskite film is an effective way to fabricate high-performance PSCs