Abstract: It is a good choice to establish an optimization model before a structural optimization. Due to the complexity of engineeringproblems, it is very difficult to construct an explicit expression ofstructural response in terms of design variables. Even though anexplicit model may be established for some problems, it would bedifficult to the problem with the model solve.Therefore, an approximation method is needed to establish an optimization modeland convert the model to a solvable one. This paper discusses some frequently used approximate modeling methods and classifies them accordingto modeling ways and methods of sensitivity analysis. The constructingmethods based on sample points, which are widely used in recently years, areintroduced in detail. Then the methods are described in applications andconcrete realization processes for structural optimizations. Advantage,disadvantage and applicable range of each method are analyzed and the trends of model establishing method for structural optimizationsin the future are pointed out.