The surface defects of HgCdTe material are one of the main reasons for the performance degradation of the detector. Focused ion beam (FIB), scanning electron microscope (SEM) and energy dispersive X-ray spectrometer (EDX) were used to study the surface defects of the CdZnTe-based HgCdTe epitaxial layer. By analyzing the reasons for the formation of different types of defects, it was determined that the defects originate from the growth process of HgCdTe material. The shape of the defect is closely related to the growth conditions. The microvoid and the volcano-shaped defects are found to be correlated to the Hg deficiency or higher growth temperature. Moreover, the collapse of the material in the molecular beam epitaxy (MBE) effusion cells may cause the instability of the beam flux, which could also contribute to the formation of the above-mentioned defects. Diamond-like defects and diamond-volcano compound defects are related to higher Hg/Te ratio and lower growth temperature. A high-quality HgCdTe epitaxial layer with a composition of 0.216 and a thickness of 6.06--7 μm was grown on the surface of a 5 cm×5 cm CdZnTe(211)B substrate. At the same time, the relationship between the types of defects and the growth process of HgCdTe thin films was established. The research results have reference significance for the preparation of high-quality HgCdTe/CdZnTe epitaxial layers.