In order to meet the demand for InSb materials in the development of mid-wave infrared detectors, InSb synthesis and zone-melting equipment is taken as the research object, and the thermal field of InSb synthesis and zone-melting is studied in this paper. The structure of the combined thermal field is studied for the two-step process, and the thermal field is numerically simulated by the finite element simulation analysis method. The temperature distribution and law suitable for the process are obtained. After the process experiment, the melting zone of 3--10 cm appears in the ingot, and the N-type InSb ingot with carrier concentration and mobility meeting the requirements is obtained. The combined and three-stage thermal field structure effectively improves the efficiency of material preparation and reduces the manufacturing cost. The results show that the temperature field distribution of synthesis and zone melting equipment meets the design requirements. The simulation results provide a theoretical basis and effective means for the optimization and improvement of such equipment, and provide a material preparation basis for the development of infrared detectors.