The theory and practice study is carried out to solve problems of stability analysis method and load factor limits for large-span abnormal RC shell roof structure. One new stability analysis method is developed in Abaqus software which can consider strength failure of concrete material. The reasonable safety factor to the concrete shell is discussed when strength failure and buckling is coupled together, and the recommended value is 2.0. Finally, the practice study is carried out with Datong theatre project as a case. The results show that strength failure of concrete material is the main failure mode to this roof structure, and the comprehensive safety factor can meet the requirements. Analysis and evaluation methods used in this paper can provide reference for other similar structures.