The dual-rotor wind turbine is an innovative horizontal axis design that harnesses the wake of the front turbine for additional power generation, leading to a higher wind energy utilization coefficient. However,the longer axial span required to minimize the flow field interference between the front and rear turbines complicates the drivetrain’s modal characteristics, raising the risk of resonance due to multi-point elastic support in the flexible frame. This study incorporates frame flexibility and elastic support into a rigid-flexible coupling dynamic model of the drivetrain using multibody dynamics. The analysis of the drivetrain’s coupling vibration modes reveals that the first two torsional vibration natural frequencies are 5.63 Hz and 6.01 Hz, corresponding to the rear and front turbine drivetrains, respectively. The drivetrain exhibits three vibration modes: local vibration in either the front or rear turbine, coupled vibration in either turbine drivetrain, and coupled vibration between both turbines. The study concludes that frame flexibility redistributes modal energy across components, affecting the drivetrain’s natural characteristics.