Abstract: The large high accuracy flat antenna framework is the key part of the phased array radar．It is characterized by large area，high accuracy and extremely difficult to manufacture．The characteristics of the large high accuracy flat antenna framework are analyzed and the main reasons of deformed welding and the way of controlling deform are discussed in this paper．The deform regularity of large high accuracy flat antenna framework for welding is obtained by welding simulation test．The solutions to control the welding deform and to improve the accuracy are adopted． The difficult problem to manufacture the large high accuracy flat antenna framework is solved．