Based on the rigid body rule, an improved plastic hinge model is adopted to produce a spatial elasto-plastic beam element for the stability analysis of the steel dome structure of LNG storage tank by the consideration of the nonlinearity of geometry and materials.Two different methods of considering initial imperfections between local load disturbance and global modal disturbance and whether to consider the influence of material nonlinearity on the stability of the structure are studied. The results show that the initial defects, material nonlinearity and reduction of restraint stiffness will all reduce the stable bearing capacity of the grid dome structure. The stable bearing capacity of the structure under load interference is sensitive to the magnitude of the interference but not to the position; the modal interference is an overall geometric defect, the overall initial deformation of the structure is large, and the load-displacement curve is smooth.Compared with ABAQUS, the elasto-plastic rigid body criterion spatial beam element and its corresponding nonlinear analysis method are more efficient and accurate. It is suitable for nonlinear analysis of large and complex engineering structures, and has advantages in dealing with the effects of local defects on the structural stability.