Perovskite solar cells (PSCs) are considered a highly promising candidate for next-generation solar cells due to their high power conversion efficiencies (PCEs). At the current stage, it remains an important and urgent task to develop continuous and reliable manufacturing technology for large-scale PSC production. Herein, we investigate an antisolvent-assisted roll-to-roll (R2R) slot die coating process to fabricate uniform and pinhole-free perovskite layers on flexible substrates. The processing parameters such as the air flow rate (Q(air); from 5 to 30 L/min) in a dryer and the solution feeding rate (Q(sol); from 0.01 to 0.05 mL/min, corresponding to the wet thickness of 0.67-3.39 mu m) in the slot die, are systematically varied to control the nucleation and the growth of perovskite crystals. Uniform MAPbI(3) perovskite films are fabricated by antisolvent-induced crystallization under optimal conditions, and the resulting PSCs show a PCE of 9.68% with low charge recombination and high absorbance. Also, to obtain higher PCEs of partially R2R-processed PSCs, a triple-cation perovskite system is applied to this one-step R2R slot die coating process for the first time, enabling a PCE of 13.41% with uniform perovskite films. Our research on the R2R process provides guidelines for obtaining uniform layers in the scalable coating of perovskite films and promotes the commercialization of PSCs.