GaSb-based nanowires in a gate-all-around geometry are good candidates for binary p-type transistors,however they require the introduction of compressive strain to enhance the transport properties.Here,we for the first time demonstrate epitaxial GaSb-GaAsxSb1-x core-shell nanowires with a compressively strained core.Both axial and hydrostatic strain in GaSb core have been measured by X-ray diffraction (XRD) and Raman scattering,respectively.The optimal sample,almost without plastic relaxation,has an axial strain of-0.88％ and a hydrostatic strain of-1.46％,leading to a noticeable effect where the light hole band is calculated to be 33.4 meV above the heavy hole band at the r-point.This valence band feature offers more light holes to contribute the transport process,and thus may provide enhanced hole mobility by reducing both the interband scettering and the hole effective mass.Our results show that lattice-mismatched epitaxial core-shell heterostructures of high quality can also be realized in the promising yet demanding GaSb-based system.