On the basis of the introduction of theoretical fundamentals, dynamic interactions in hydraulic pipeline systems are studied using different simplified simulation methods. Simulation results of the concentrated parameter method, the distributed parameter method and the transfer matrix method are represented and compared with each other as well with the help of Bode analyses of magnitude and phase in the frequency domain.By flow simulation, the internal flow processes in a hydraulic pressure relief valve and a servo valve are investigated under different calculation conditions with the aid of CFD. The analyses of turbulent flow, the cavitation phenomenon under steady and unsteady condition and dynamic opening and closing process of the pressure relief valve are carried out using the corresponding turbulent-, multiphase- and dynamic meshing model provided in the CFD commercial code - FLUENT. Studies of the distributions of various parameters, e.g., static pressure, velocity magnitude, velocity vector and volume fraction of vapor especially for the evaluation of the cavitation are carried out under the corresponding computing conditions.