In spite of the outstanding photoelectric properties of perovskite materials, numerous defects produced in the preparation process eventually result in decomposition of the perovskite layer. To date, the mechanism of defect passivation and hysteresis reduction via additive engineering has still been obscure for perovskite materials, which seriously restricts performance improvement of the devices. Herein, conductive atomic force microscopy (C-AFM) and Kelvin probe force microscopy (KPFM) measurements were applied to probe carbamic acid ethyl ester (EU)-based trap passivation and suppression of hysteresis in perovskite films. The results indicate that the internal interaction between multifunctional bonds ("CO" and "-NH2") of EU and Pb2+ ions of the perovskite may inactivate the trap state and inhibit ion migration within sub-grains and grain boundaries (GBs), resulting in improvement of the long-term stability of the cells. In consequence, the EU-modified champion device prepared in all-air achieved a power conversion efficiency (PCE) of 20.10%, one of the high performances for the devices fabricated in air to date. In short, this work will propose some interesting speculation about ion migration as well as its influence on hysteresis in perovskite materials.