Stroke is a neurological disease and is a significant cause of disability throughout the world. Patients with stroke or post-stroke usually still experience interference in walking in the form of a drop foot caused by atrophy of the anterior tibialis muscle, so they cannot perform dorsiflexion. Drop foot disorders can be treated by rehabilitation using Posterior Leaf Spring Ankle-Foot Orthosis (PLS AFO). PLS AFO has the advantage of a higher level of flexibility compared to other AFO types. The primary purpose of this research is to observe the level of resilience based on the influence of AFO thickness. This study uses the finite element analysis of three model variations in the initial contact, midstance, terminal stance, and calf loading phases. The material used in this study was carbon fiber. The simulation will result in the distribution of stress, strain, and deformation values in each AFO model. The simulation results show that AFO resistance is affected by variations in AFO thickness where the increase in strength is proportional to the increase in AFO thickness. The AFO with a thickness of 10 mm is the most suitable for the tibialis anterior atrophy case.