This article presents the study of the Jeffcott rotor shaft system, diameter 32 mm, length 1000 mm with a disc in the middle of an exterior diameter 250 and 30 mm thickness for four different materials namely (JIS-S45C steels, 38CrMoAl steels, structural steels, titanium steels (Ti-6AL-4V)), for a case simply supported, and it is important to determine the natural frequencies, critical speeds and amplitudes of the rotor system (von Mises stress, principal stress, maximum shear stress, lifetime). This characteristic is found by using the parametric design tool ANSYS Workbench. Modal, harmonic cases are realized for the single-rotor system. The results obtained for this analysis are useful for design of rotor system and to facilitate engineering applications and allied researches by presenting a detailed comparative picture based on dynamic analysis of Jeffcott rotor. The authors covered modal, harmonic response along with natural frequencies and whirling speeds at different modes. Resonance occurrence speeds are also analyzed using the Campbell diagram. The harmonic response is investigated, with added material (0.1 kg) on the disc, to reveal the von Mises stress, normal elastic strain, total displacement, maximum shear stress and life cycle number. FEA is carried out to estimate critical speeds for these four materials. The results of this study indicated that the critical speeds are superiors for 38CrMoAl steel, (1858.7, 1859.4, 8468.1 rpm) and lower for the steels of JIS-S45C (1784.2, 1784.9, 8147.7 rpm) by contribution the two steels (structural steels, titanium alloy (Ti-6Al-4V)). The natural frequencies of the Jeffcott rotor are also higher for 38CrMoAl steels and are equal for the two materials (Titanium alloy (Ti-6Al-4V), JIS-S45C) and minimum for structural steels. On the other hand, the results of the harmonic analysis indicated that the vibration severity is very lower for 38CrMoAl steels material (9435.2 MPa) and very higher for structural steels material (55134 MPa). The rotary machines undergoing high stress severity and deformation severity are recommended to use 38CrMoAl steels. Rotor dynamic analysis of Jeffcott rotor with four materials, JIS-S45C, 38CrMoAl, structural steel, titanium alloy materials are highly recommended with the less severity of vibration. Choose JIS-S45C and 38CrMoAl materials for higher whirling speeds compared to structural steel, titanium alloy materials. The rotary machines undergoing higher operating speeds like propeller shafts, turbine and compressor are recommended to use JIS S45C and 38CrMoAl.