Abstract. The aim of this paper is numerical analysis of plain journal bearing with Nano particle added lubricating oil. The fluid film bearing is studied with the modified Reynolds equation which considered time dependent inertia effects at rotating speeds with the linearized turbulence. The research is performed for numerous nano-fluids include nanoparticles of CuO, TiO 2 , Ag and Cu and SAE 20W50 as a base fluid. The time transient governing equations include the incompressible mass conservation equation, Navier-Stokes momentum equations for thin film lubrication, and full kinematic including shaft accelerations are solved numerically. Two cases of long and short bearings are studied with Sommerfeld and Gumbel boundary conditions. Linearized force coefficients such as mass, stiffness and damping factors are obtained for an ordinary journal bearing. The ordinary plain journal bearing velocity response and the rotor displacements when sudden forces applied by rigid rotor symmetrically is achieved. The results prove that using the nanoparticle enhanced lubricant causes higher mass coefficients, damping ratios and fluid effective stiffness.