Purpose: This study aimed to evaluate distribution and maximal value of mechanical stresses on the reconstruction plate, bridging mandibular symphysis defect, and to optimize the most appropriate locations of the plate to distribute the stress causing the fracture of the plate. Materials and methods: Four types of reconstruction were constructed by different number and location of the reconstruction plates on the 3 D finite element model (FEM) of a human edentulous mandible; Type I: one plate on the inferior border of the anterior mandible, Type II: one plate on the middle of the anterior mandible, Type III: one plate on the superior border of the anterior mandible, and Type IV: two plates on the inferior and superior border of the anterior mandible. Results: The results showed that the maximal stress of type I (234.29 Mpa) was lower than that of type II (260.91 Mpa) and type III (247.37 Mpa), but higher than that of type IV (186.64 Mpa). We could also observe that the stresses are tending to focus on the inner side and inferior part of the plate which connected proximal segment from the vertical load. Conclusions: On the basis of the findings, it was concluded that using a plate on the inferior border of mandible or two plates on the inferior and superior border of mandible are more favorable to distribute mechanical stresses, which could reduce the fracture of the plate.