The cylindrical gear with arcuate tooth trace has advantages of high bearing capacity,high contact strength and steady transmission,etc.But there are also failure modes such as the wear of tooth surface,pitting and scuffing when it drives,it is mainly because of the bad lubricating condition.So ensuring that it is always in good lubricity would be critical.After analyzing the meshing contact process of cylindrical gears with arcuate tooth trace,the contact model of gears is simplified.Based on the elastohydrodynamic lubrication theory,the physical and mathematical model of isothermal elastohydrodynamic lubrication for the cylindrical gear with arcuate tooth trace are established.Through the direct iterative method and Fortran procedure,the numerical solution of the model is solved and the characteristic curves of oil film are got.The influences that entrainment velocity,load and viscidity bring to lubrication characters of the cylindrical gear with arcuate tooth trace are analyzed and compared.The results show the entrainment velocity is the most important cause for the oil film thickness,the viscidity has important influences both on the oil film pressure and thickness,and the load influences less relative to other two factors.Besides,using the oil film thickness ratio,the lubrication state of gears could be estimated,which helps keeping gears approach the elastohydrodynamic lubrication state when designing.