For frequent cracking of pantograph upper arm rod in its service,the pantograph-OCS coupled method of multi-rigid-body or lumped-mass model is mainly used for analysis.However,this method fails to reflect the influence of flexible vibrations of key components on dynamic responses and fatigue damage.To address this issue,a flexible pantograph-OCS coupled dynamic model was de-veloped based on multi-body dynamics,finite element method,and modal reduction technique to account for the flexibility of upper arm rod.The influence of the flexible model on contact force and structural response was investigated.According to the results,compared with the rigid-body model,the flexible model leads to the increases of 2.88%and 3.74%in the mean and maximum contact force,respec-tively,while the minimum value decreases by 58.64%,with only a slight change in the standard deviation.Pronounced resonant respons-es of the upper arm rod were observed around 140 Hz and 320 Hz,where 320 Hz corresponds to a higher-order mode,resulting in the in-creases of 43.96%and 44.81%in the maximum value and standard deviation of the pantograph bow acceleration,respectively.Further-more,fatigue analysis based on the rainflow counting method shows that the cumulative damage predicted by the flexible model is ap-proximately 62.55%higher than that of the rigid-body model,indicating that resonance significantly accelerates damage accumulation.These results demonstrate that the flexibility of the upper arm rod affects high-frequency dynamic responses and load distribution charac-teristics,thereby significantly influencing both the pantograph-OCS interaction and the fatigue behavior of critical components.The pro-posed model provides a theoretical basis and methodological support for refined dynamic modeling of pantograph-OCS system,fatigue strength evaluation of key components,and in-service condition monitoring.