BACKGROUND:: The location of residual dentin may affect stress distribution of tooth root. OBJECTIVE:: To make a three-dimensional finite element analysis of gold alloy post-core and all-ceramic crown in the repair of structure defects of the mandibular first molar, and to provide a guideline for planning restoration for such kind of tooth structure defects. METHODS:: Three-dimensional finite element models of the restored first mandibular molars were constructed by CT image reconstruction technique. Then MIMICS software was used to separate the areas and finish the three-dimensional calculation. GEOMAGIC software was also applied to modify and generate a NURBS surface in each patch. All components of the models were assembled under the ANSYS preprocessor. The Mohr strength theory was applied for comparing the maximum Mohr stress value of dentin and stress concentration areas in six models under different simulating loads. RESULTS AND CONCLUSION:: The restoration effects in six models were compared, the maximum Mohr stress value of dentin and stress concentration areas were not obviously different. The location of residual dentin has little influence on the stress value and distribution, when restored by gold alloy post-core and and all-ceramic crown. Funding: the Science and Technology Development Plan of Jining City, No. [2011]57 SUBJECT HEADINGS:: tissue engineering; tooth; mandible; dentin