A grand challenge problem of the plant biology is to elucidate the regulation mechanism of mechanical properties of cell walls. Primary cell wall provides sufficient strength to withstand turgor pressure as well as the functionality of orchestrating expansion to accommodate enlargement of the individual cell. From decades of studies, knowledge on the composition of cell wall has matured. On the other hand, how those components are put together to provide such competing functionalities is yet to be understood. Advances of biochemical analytical methods provided a wealth of knowledge that is full of insights. Nonetheless, the hypothesized molecular structure's mechanical consequences are not easy to understand. Such knowledge is important in engineering processes of biomass; especially in the field of bio-based renewable energy production. This study employed the finite element method which models cell wall components at the nano scale where molecular interactions are modeled with surrogate mechanical finite elements. Owing to the nature of finite element method that results in a model at a larger scale than individual element, the overall cell wall structure model's mechanical behavior emerges from mechanical properties and interactions of elements at the underlying scale. Using this approach, a number of hypothesized cell wall structures were examined from the classical mechanics standpoint, including the number of cellulose microfibril-hemicellulose interconnections, biochemical interactions between cellulose microfibril and hemicellulose, and changes of mechanical stiffness of the cell wall components as a result of biochemical modifications. This study demonstrates an engineering approach contributing to the fundamental plant biology science.