A　controllable　ferroelastic　switching　in　ferroelectric/multiferroic　oxides　is　highly　desirable　due　to　the　non-volatile　strain　and　possible　coupling　between　lattice　and　other　order　parameter　in　heterostructures.　However,　a　substrate　clamping　usually　inhibits　their　elastic　deformation　in　thin　films　without　micro/nano-patterned　structure　so　that　the　integration　of　the　non-volatile　strain　with　thin　film　devices　is　challenging.　Here,　we　report　that　reversible　in-plane　elastic　switching　with　a　non-volatile　strain　of　approximately　0.4%　can　be　achieved　in　layered-perovskite　Bi2WO6　thin　films,　where　the　ferroelectric　polarization　rotates　by　90　degrees　within　four　in-plane　preferred　orientations.　Phase-field　simulation　indicates　that　the　energy　barrier　of　ferroelastic　switching　in　orthorhombic　Bi2WO6　film　is　ten　times　lower　than　the　one　in　PbTiO3　films,　revealing　the　origin　of　the　switching　with　negligible　substrate　constraint.　The　reversible　control　of　the　in-plane　strain　in　this　layered-perovskite　thin　film　demonstrates　a　new　pathway　to　integrate　mechanical　deformation　with　nanoscale　electronic　and/or　magnetoelectronic　applications.