At present, the demand for large-format HgCdTe infrared focal plane array(IRFPA)detectors continues to increase, and the development of larger HgCdTe material technology has become a research hotspot. The 4 in silicon-based HgCdTe epitaxy technology is studied. Through a series of measures such as improving the stability of equipment parameters, controlling the flatness of epitaxial wafers, and optimizing material process parameters, the key technical bottleneck of the large-size silicon-based HgCdTe material process has been broken through. 4 in silicon-based HgCdTe materials with low flatness, high uniformity, low defect rate and high quality are obtained. The results show that the material′s full width at half maximum(FWHM)is not more than 90 arcsec, the surface macro defect density is not more than 100 cm-2, and the surface flatness is not more than 15 m.