Miniplate osteosynthesis has become a standard treatment of mandibular fracture treatment and reconstruction in oral and maxillofacial surgery. To avoid postoperative mechanical loosening of screws caused by excessive loads, it is important to determine the nature of stress distribution in the bone surrounding the biomaterials. Numerous biomechanical studies of implantation have revealed that there is a direct correlation between high-stressed region and bone resorption. In particular, loosening of screws and bone resorption is associated with high peak stresses at the interface in the immediate postoperative stage. To investigate the biomechanical behaviour of bone tissue in case of bone fractures in terms of load transfer and stain-stress distribution in the bone/fixation system, finite element model of the fractured mandible was developed. The mandible compact bone was modeled as an orthotropic, heterogenous, composite material, but cancellous bone – as isotropic, homogeneous material. Titanium was taken as material for fixation system. The fracture gap was modeled as a thin layer of material with varying properties during the bone healing period. The developed finite element model was loaded with multiple force vectors to simulate muscle forces over wide areas of attachment. Groups of parallel vectors simulated eight pairs of masticatory muscles (superficial and deep masseter, anterior, middle, and posterior temporalis, medial and lateral pterygoid) assumed to be directly attached to bone. The model was evaluated taking into account the effect of bite force values and fracture healing stages. The calculated stresses and strains showed that in the fixation system with the chosen shape and dimensions there was no risk of fracture due to fatigue or plastic deformation. However high values of bone tissue strains and displacements indicated that the device used could not provide the necessary fracture fixation at the initial stage of healing. In view of finite element analysis results it was recommended to improve the fixation system by using two plates. This analysis may be useful in evaluating new plate geometry, length and diameter, as well as shape or design and material properties of the fixation plates.