In order to investigate the nonNewtonian effect of elastohydrodynamic lubrication (EHL),the EHL characteristics difference between Newtonian fluid and nonNewtonian fluid in steady state and timevarying condition was discussed.The lubricant was assumed to be a ReeEyring nonNewtonian fluid,and the effects of entrainment velocity,slideroll ratio,the maximum Hertzian pressure and the characteristics shearing stress on the EHL performances were studied.The timedependent EHL performance of nonNewtonian fluid was analyzed,and was compared with that of Newtonian fluid.Results show that,under isothermal and light load conditions,the increasing in the entrainment velocity leads to a sharp second pressure peak for Newtonian fluid,and the increasing of the entrance film thickness for nonNewtonian fluid,especially under the condition of large slideroll ratio.Under the condition of high speed and large slideroll ratio,the lighter the load,the more apparent the nonNewtonian effect.Under the timevarying condition,the entrainment velocity fluctuation has a great influence on both Newtonian and nonNewtonian fluid,the second pressure peak of the nonNewtonian fluid is always smaller than that of the Newtonian fluid at each instant.Therefore,dynamic effects and nonNewtonian effect should not be ignored for the study of isothermal point contact EHL.