Using RHEED as a real-time monitoring tool, the MBE temperature measurement system was calibrated according to the relationship between GaAs (100) surface reconstruction phase and the substrate temperature, As4 beam equivalent pressure of the substrate. This approach can also be applied to other MBE systems. It provides an experimental basis of the growth of high-quality epitaxial thin films for studying of the surface roughness of InGaAs, the phase transformation process and the surface morphology.