The most frequent cause of defect in the mandible is tumor-related surgery. Larger defects cause severe morbidity due to disturbances in function and esthetics. A fibular free flap is one way of filling a bony hole in either the upper or lower jaw. It is one of the common ways of replacing bone that has been removed for cancer treatment. Doctors use a free fibular flap which is grafted from the patient who needs a transplant operation to fit the defect. In this study, a new method combining preoperative planning and rapid prototyping for mandibular fibula free flap reconstruction after tumor surgery was made based on Mimics software simulating surgery on a workstation. The preparatory work of surgery is divided into two parts: software simulation and model building. During software simulation the authors were able to choose the best site for the osteotomies regarding circulation and the model building can increase the precision and speed of treatment. A description of our surgical approach is presented and is supplemented by an illustrative case.