For fabricating long wavelength HgCdTe material,CdTe/InSb composite substrate was grown by molecular beam epitaxy(MBE). Two difficult problems of InSb oxide layer removal and In material diffusion control was solved through experimental research and technical analysis. Secondary oxidation of InSb substrate can be prevented by growing As passivation layer on InSb substrate before InSb substrate transfers from III-V cavity to II-VI cavity. In material diffusion can be prevented by adjusting the thickness of As passivation layer under common annealing process.