To strengthen guarantee level of Distance Measuring Equipment FSD-40/45, so as to improve operation quality of navigation equipment, though the testing of the DME of southwest air traffic management and the testing verification of the DME FSD-40/45 of Chengdu regional management, and the analysis on DME FSD-40/45 technical manual, the path design of DME FSD-40/45 is summarized, so the fault investigation efficiency of DME FSD-40/45 equipment can improved by use for reference of these experiences.