Various studies recommend that threaded type implants should be used to maximize initial contact, improve initial stability, enlarge implant surface area, and favor dissipation of interfacial stress. The objective of this study was to compare four types of screw implants placed in posterior region of mandible model and evaluate the influences of implant shape, configuration, length, diameter and abutment connection method on stress distribution using a three-dimensional finite analysis. Four types of two-length implant models — 8.5 and 13 mm — were selected and the wide diameter was also used. Four groups were classified by implant outline and connection manner A load of 100 N was applied vertically on the center of the implant. Oblique and horizontal loads were taken as equal to that of the vertical load. The TMJ area in mandibular model was constrained in all directions. Results show that the stress of two-length implants was similar in all groups and the internal connection implant with appropriate thickness of inner part of the implant had better stress distribution.