A torsional vibration dynamic model of double-cardan shaft is established with tools of constraint equation and finite element method.Numerical simulation shows that angular accelerations of the model are identical with calculation results
verifying the correctness of double-cardan shaft.The fluctuation of mid-shaft due to corner angle of cardan and high frequencies of torsional vibration are considered in this model and it is suited for torsional vibration analysis of cardan shaft drive system.