Abstract: The large construction equipment cannot be used to replace large components in the radome due to the compact space. To solve this problem the replacement technology of large antenna secondary reflector and feed source in the radome is studied in this paper. The construction method of lifting and replacing the secondary reflector and the feed source at the top of the large antenna in the radome is realized by using the pitching movement of the antenna itself in the lifting and combining the advantages of long-distance lifting of the electric hoist. By optimizing the construction process and analyzing the stress of the key positions, a set of feasible construction methods are formed and the replacement of large secondary reflector and feed source is successfully completed. The final structural and electrical technical indicators of the antenna meet the requirements. This method has been applied to the modification of the secondary reflector and the feed source of the large antenna in the radome for the first time, which can provide practical guidance for the subsequent on-site modification of the large antenna.