Abuse conditions of torsion and vibration occurred on crankshaft should be eliminated or diminished during the engine design process. 3D model of the crankshaft is set up by means of the simplified crankshaft system, using the concentrated quality method. FEA software was used for analyzing the different vibration amplitude orders. Two models with absorber and without absorber were compared and tested. The results of torsional vibration amplitudes-speed and so on are benefit to the new product development for eliminating the potential mechanical harm.