Safety protection design is a key problem to be considered in structural design. The study on mechanical characteristics of rolling lobe air spring（RLAS） under the extreme working condition lays an important foundation for its safety protection design. Considering the influence of outer diameter of rubber bellows along with the height of air spring, taking the radius of arc segment and inner cone angle of linear segment as the key design parameters, a novel mechanical model of rolling lobe air spring with safety protection design is established. The experimental results show that the maximum relative error of structural parameters of rolling lobe air spring is 11.9%, the relative error of static stiffness under different pressure in the extreme condition is less than 11% and the maximum relative error of load capacity is less than 6%, which all proves the correctness of mechanical model of RLAS. Force gain and stiffness gain are further proposed as quantitative characterization indexes of safety protection design, and the influence laws of key design parameters on mechanical characteristics and quantitative characterization indexes of rolling lob air spring under extreme condition are explored. The research results provide theoretical support for accurate calculation of safety protection capability of RLAS in the design stage.