In order to reduce the influence of the defects of telluride cadmium mercury (HgCdTe) thin films grown by liquid phase epitaxy (LPE) on the performance of infrared detectors, a special type of surface defects, the frustum-shaped defect, was systematically studied by means of scanning electron microscopy, energy dispersive X-ray spectrometer, focused ion beam and comparative experiments. The size of these defects ranges significantly, from approximately 150 to 400 micrometers, and under an optical microscope, they exhibit a morphology resembling a frustum with a concave center. Compositional analysis revealed no significant differences between the surface of the defect and the normal film morphology. Further analysis of the interface between the tellurium zinc cadium (CdZnTe) substrate and the HgCdTe film indicated that these penetrating defects orginate from triangular telluride inclusions with central holes on the CdZnTe substrate, and the size of tellurium inclusions is almost above 20 μm. Therefore, by improving the quality of the CdZnTe substrate and enhancing substrate screening, the frustum-shaped defects in HgCdTe films can be reduced, thereby improving the quality of HgCdTe epitaxial materials. This enhancement is essential to meet the demands of high-performance infrared detector development.