Buried interface engineering is essential for improving optoelectronic properties and the charge extraction process to achieve high efficient perovskite solar cells (PSCs). Herein, we designed and prepared the 4-Sulfamoylbenzoic acid (Sba) functionalized MXene (MX-Sba) nanosheets to modify buried interface of PSCs. Such functionalized strategy enabled the MX-Sba to form a double-sided association with SnO2 and perovskite to passivate both-side defects due to the coexistence of F groups within MXene and NH2 and SO groups of Sba. Compared to the MXene, MX-Sba not only further improved the conductivity of SnO2 layer, but also helped to achieve the desirable interfacial band arrangement. As a result, the MX-Sba based PSCs achieved the highest photoelectric conversion efficiency of 23.49 % with improved stability. This work provides an effective strategy for buried interface engineering in PSCs, which is also applicable for other photoelectric devices.