Organic-inorganic perovskite solar cells emerge as one of the most promising photovoltaic technology due to its high performances. Particularly, inverted perovskite device architecture, due to low temperature processing, have a great potential in commercialization. High-crystalline quality perovskite film and interfacial passivation are essential to yield high performance devices. In this work, we employ a simple strategy of using molybdenum disulfide (MoS2) as both the interfacial layer and the additive to prepare efficient PSCs. MoS2 as an additive in perovskite can form the CH3NH3PbI3:MoS2 heterostructure, resulting in the homogeneous perovskite film with larger crystal grains. In addition, MoS2 as the buffer layer (BL) between poly (3,4-ethylene dioxythiophene)-poly (styrene sulfonate) (PEDOT:PSS) and perovskite can prevent the decomposition of perovskite film by avoiding the direct contact with the hydrophilic PEDOT:PSS films. On tedious optimization, the champion device based on active layer of CH3NH3PbI3:MoS2 (10 v%) as well as employing MoS2 buffer layer shows a remarkable improvement in the power conversion efficiency (PCE) (from 15.29% to 18.31%) and a better stability, with 87% of the initial efficiency sustained after 20 days. Our finding herein provides a promising way to fabricate high efficiency and stable photovoltaic devices.