The thermal conductivity of germanene is calculated using the equilibrium and the non-equilibrium molecular dynamics simulations. Firstly, the thermal conductivity of germanene is simulated by the equilibrium method, and the components of thermal conductivity decomposition are further calculated. Unlike graphene, the thermal conductivity of germanene is small and the component is dominant. Secondly, the non-equilibrium method is used to simulate and calculate the thermal conductivity of a series of lengths of germanene. It is obtained that the thermal conductivity of the convergence with the non-dependent length by fitting. Finally, it is found that not only on the numerical results are consistent by comparing both the equilibrium and the non-equilibrium methods, and the simulation data of the equilibrium can be transformed into a length dependent relation by fitting the phonon group velocity, which can also be overlapped with the non-equilibrium data points. Therefore, we have determined that the thermal conductivity of germanene are effective and equivalent, which are calculated using the GPUMD package based on both the equilibrium and the non-equilibrium methods.