This study aimed to construct throe-dimensional finite element model of the mandibular complete overdenturo and to analyze the influence rules for stress distribution under different mandibular shapes. The layer cutting method was employed as a basic tool to deal with different plaster models to gain two-dimensional point data. These data were introduced to the commercial software ANSYS to construct throe-dimensional finite element model of the mandibular complete overdenturo, including nine kinds of typical shapes, such as sharpness, roundness and squareness, and etc. Static loads were imposed on denture so as to accomplish biomechanicel analysis and to study the influence rules of stress distribution for mandibular complete overdenturo under different mandibular shapes. Results revealed that the sequence of stress from high to low was squareness, roundness, sharpness and the other extrapolated, basic and inside. The throe-dimensional finite element model has high simulation accuracy and the results provide an experimental foundation and guidance for clinical work.