Basic loads applied on the airship envelope were analyzed. The resultant forces, the static bending moment and the dynamic bending moment were formulated. Based on classic linear elastic membrane theory, the procedures to calculate the minimum pressure were proposed for sufficient rigidity evaluation. The limit load capacity was further investigated, and the related formula were developed. Finally, the stress and internal forces analysis was carried out for cylindrical and non-cylindrical approximations of envelope hull of airship. The present research is very valuable to the overall preliminary design of airship and further research.