DME is a short-range radio navigation system stipulated by ICAO. In actual use, ranging error may occur in some coverage airspace. After analysis and verification, the factor of radio interference is excluded, mainly due to the zero-zone caused by terrain reflection. This paper mainly analyzed and simulated the distribution of the zero-zone of the DME antenna radiation pattern through the analysis of the two-path interference effect of the DME system. It provides theoretical reference for the selection of DME ground beacon and the height determination of antenna erection.