This book focuses on numerical simulation-based design theory and methods in mechanical engineering. The simulation-based design of mechanical equipment involves considerable scientific challenges including extremely complex systems, extreme working conditions, multi-source uncertainties, multi-physics coupling, and large-scale computation. In order to overcome these technical difficulties, this book systematically elaborates upon the advanced design methods, covering high-fidelity simulation modeling, rapid structural analysis, multi-objective design optimization, uncertainty analysis and optimization, which can effectively improve the design accuracy, efficiency, multi-functionality and reliability of complicated mechanical structures. This book is primarily intended for researchers, engineers and postgraduate students in mechanical engineering, especially in mechanical design, numerical simulation and engineering optimization.