Clinically, many implant cases with different angulation over the lower posterior area have been found. The purpose of this study was to analyze the bony stress with different implant tilting during normal masticatory load using the finite element method (FEM), with the hope of discovering a desirable installation of implant. A three-dimensional finite element method was employed to analyze the bony stress generated by different angulation designs (15 degrees) of implant bodies. Eight solid models of the mandibular first and second molars were built up and then transferred to a mesh model in FEM (ANSYS) to perform a stress analysis. A simulated load (400 N) was applied to the splinted crowns with vertical and horizontal forces. The loading sites were on the central fossa of the splinted crowns. For stress distribution, some designs will be better than a parallel installation. The results suggested that not all implant bodies tilting with the splinted crowns lead to stress concentration.