Abstract: The interband transition of GaSb/In_xGa_1-xAs_0.02Sb_0.98m quantum well structure has been calculated by using one dimensional rectangular quantum well model.The critical layer thickness of this material system has also been calculated based on energy balance model.It is shown that GaSb/InGaAsSb is a suitable material system for 2-3μm mid-infrared quantum well lasers.It is very important to adopt suitable composition and well width,and to control the total amount of strain in the structure design and material growth.