Abstract: A new etchant consists of hydrofluoric acid, peroxide and tartaric acid for the chemical etching of GaSb/AlGaAsSb materials has been studied. Results show that this etchant has a stable etching rate to both GaSb and AlGaAsSb compound materials; under suitable solution composition quite low etching rate could be obtained, which are useful for the fabrication of GaSb/AlGaAsSb devices. Parabolic relation between the etching rate of AlGaAsSb materials and their Al content was found, unselective etching could be performed for GaSb and AlGaAsSb material with certain Al content.