To assist engineers in enhancing the design aesthetics of complex products with exposed structures, this study investigates the mapping mechanism between form features and style images of complex products, taking aero-engines as an example. First, factor analysis is employed to identify the adjectives which can accurately describe the style of aero-engines. Next, the form features of exposed components are extracted through expert interviews. Then, the 113 different aero-engines are evaluated for style image ratings and assigned component attributes, and the data are analyzed using multiple regression analysis. Finally, the mapping model between the component features and style images is constructed. The results indicate that the surface quality of components and the interrelations between components are the key factors influencing the style images. The findings of this study assist engineers in designing the appearance of complex products with exposed structures and provide a feasible methodology for the design of the products.