OBJECTIVE The changes of the location and force of the condyle influenced by occlusal splint were investigated in order to know the biomechanical mechanism of occlusal splint therapy. METHODS Auto-CAD technology, CT scanning, computer imaging analysis measurement and finite element method were separately used to comparatively analyze condylar position and its stress distribution in patients with temporomandibular joint disorders (TMD) treated with or without occlusal splint. RESULTS Occlusal splint could lessen anterior space, in crease posterior and upper space in the temporomandibular joint (TMJ), so the condylar position move anterioinferiorly; the stress on condylar surface was lowered, mainly in anterior oblique surface or lateral side of condylar loading position; and the stress symmetry was bilaterally improved. OCCLUSION: The study suggests that regulating condylar position and improving the stress distribution is considered one of biomechanical mechanism of occlusal splint treatment.