High quality GaAs/GaAsSb superlattices were grown by molecular beam epitaxy (MBE) and the Sb/As exchange action was characterized by high resolution X-ray diffraction (HRXRD). The Sb desorption from the GaAs surface increases with the increase of substrate temperature, causing a net decrease in Sb composition. The Sb flux and the Sb soak time have no obvious effects on the Sb/As exchange. It is shown that the exchange action was restrained on the surface and the Sb diffusion in GaAs was limited