*

This study explores the strain effect on the ferroelectric properties of a monolayer CuInP2S6 , which can greatly impact the performance of the emerging van der Waals ferroelectric devices such as the ferroelectric tunnel junctions, ferroelectric random-access memories, and ferroelectric field-effect transistors. By employing density-functional theory calculations, we elucidate the effects of strain on the electronic structures and ferroelectric properties of the material. The underlying mechanism of such strain engineering is revealed through an analysis of strain-dependent formation energy, charge distribution, density of states, and more. These findings highlight the potential of strain as a tool for lowering transition barriers and facilitating ferroelectricity switching via an electric field, thus enhancing the performance of monolayer CIPS in energy-efficient devices.