It is essential to investigate nanomechanical behaviors of cytoskeletal actin filaments in order to understand their critical roles in various cellular functional activities. Experimental observations indicate that mechanical stimuli on actin filament likely modulate affinities of actin filament to its binding proteins. Therefore, actin filament is regarded as a mechanosensor at the molecular level in the cell. In this study, to obtain better understanding of the mechanism of the mechanosensoring process of actin filament, we perform a large-scale molecular dynamics (MD) simulation for a half-turn structure of an actin filament with and without tensile loading, and discuss conformational changes at specific amino acid residues which are binding sites for an actin binding protein under tensile force.