Abstract: The probability optimization of frameworks subjected to various loads is studied in this paper. A mathematic model is constructed, in which members' cross-section areas are taken as design variables, and the minimum structural weight is regarded as object function The constraints consist of the reliability of displacement and stress as well as the lower bound of the design variables. The reliability constraints are equivalently into conventional ones, and the compact constraint tactics are used to treat the constraint functions. The zigzag approach is used in search of the solution Examples show that the design model and the method presented in this paper are rational and efficient.