The presently achieved research results are not effective for the design of complex mechanical products when various methods and tools in different schemes have to be employed at different design stages. A new integrated framework for the optimal design of complex mechanical products is introduced in this research considering modeling, simulation, and optimization aspects. First, a hybrid scheme is developed for the integrated modeling of complex mechanical products. In this hybrid scheme, descriptions of a generic product are modeled by an and-or tree. Feasible design candidates are created from the and-or tree through tree-based search. Geometric descriptions in a design candidate are associated with a computer-aided design (CAD) system. Second, a hybrid simulation method is developed for the evaluation of different product aspects with different simulation tools which are integrated through the hybrid modeling scheme. Simulations with geometric descriptions are conducted by analysis functions of the CAD system. Simulations with non-geometric descriptions are conducted by the knowledge-based systems. Third, a hybrid optimization method is developed to identify the optimal design of the complex mechanical product. For each design candidate, parameter optimization is conducted to obtain the optimal parameter values. The optimal design solution is identified from all design candidates through configuration optimization. A prototype system has been implemented for conceptual design and detailed design of complex mechanical products.