Abstract: Following the Lagrangian Coordinate Method, the deformed configuration was used as a reference in order to build an accurate strain/displacement geometry. The balance equation was created using the principle of virtual work, and the accuracy and stability of the solution was ensured by using the Updated Lagrangian Formulation. The uncertain parameters which are introduced during the analysis and optimization of the aerated flexible membrane structure are portrayed using interval mathematical theory. The interval reliability optimization of an air-supported flexible membrane structure is developed based on the interval uncertainty optimization model. In this way the reliability of the membrane structure under complex conditions is improved and the probability of structural failure is reduced.