For a long time the bacterial cell division process was considered to be a lot simpler than the eukaryotic cell division. However, as more and more bacterial division proteins are identified, their functions and mechanisms remain largely elusive. For example, the essential, most well-conserved bacterial division protein, FtsZ, is thought to both provide constriction forces to reduce the radius of the division site, as well as recruiting other division proteins. Despite its central role in cell division, little is known about how FtsZ carries out these tasks. We employed a physics-based computational method (all-atom molecular dynamics simulations) to probe the structural dynamics of the smallest polymerized unit of FtsZ: a FtsZ dimer. We found that the FtsZ dimer structure can undergo a drastic structural transition during hydrolysis that shifts its degree of curvature. Such structural transition is demonstrated to derive a significant amount of mechanical force that is sufficient for cell division, thereby providing a molecular explanation for the role of FtsZ as a force generator.