The impact of posterior tooth loss on the temporomandibular joint (TMJ) is controversial. Existing studies mainly rely on clinical observation, lacking biomechanical research. This study recruited 10 healthy volunteers (Control group) and 20 patients with posterior tooth loss (PTL group). Three-dimensional maxillofacial models were reconstructed. Finite element analysis showed stress concentration in the PTL group, with stress magnitudes much higher than the Control group, especially on the tooth-missing side. Posterior tooth loss causes asymmetric TMJ stress and higher stress levels, related to symptoms of temporomandibular disorders.