OBJECTIVE: To investigate the effect of different microplate spacing on the relative displacement of the fractured mandibular ramus during mastication after using double microplates for fixation, using finite element analysis. This study aims to provide a theoretical basis for clinical design of the distance between two microplates. METHODS: Finite element models of the mandible, teeth, periodontal membrane, and microplates (Johnson & Johnson, thickness 1 mm) were established. A fracture line was set on the mandibular ramus from the sigmoid notch to the angle of the mandible, corresponding to the type I fracture line of the mandibular ramus. The experiment designed the distance between two microplates into 22 groups, with 2 mm as the initial distance and an increase of 1 mm per step, gradually increasing the distance between the two microplates to 23 mm. Friction contact was set between the two fracture fragments, and the bilateral condyles were fixed. A bite force of 230 N was applied to the bilateral first molars, and the relative displacement between the two fracture fragments under this load was calculated. RESULTS: The results showed that as the distance between the microplates increased, the relative displacement gradually decreased, from 0.46751 mm at a distance of 2 mm to 0.105789 mm at a distance of 23 mm. The relative displacement at a distance of 20 mm was 0.147448 mm, which was below the clinical critical value of 0.15 mm for the direct healing. CONCLUSION: After using double microplates for fixation of mandibular ramus fractures, the stability of the fracture fixation during mastication increases with the increase in the distance between the two microplates. At a distance of 20 mm, While theoretically capable of achieving the criteria for direct healing, further clinical validation remains necessary.