Abstract: A flexible multi-body system dynamics model of crank system is established based on ADAMS with the purpose of modeling the crank in internal-combustion engine accurately.The film hydrokinetics model is built up through linking ADAMS and elasticity hydrokinetics subroutines.Coupling analysis between multi-flexible body system dynamics and hydrodynamic lubrication of crank system is processed.Results between the model with the function of film and without the function are compared.Then the journal center loci are given.The effects of different factors such as pressure,temperature,rotating speed and load on the journal center loci are also analyzed.