In order to verify the principle of the prototype design plan of the cylinder direct acting riser tensioner system, cosimulation models of the pneumatichydraulic circuit and multibody mechanical system are built based on the multidisciplinary simulation software SimulationX. The dynamic response analysis was carried out on the tensioning system under three working conditions of normal operation mode, two symmetrical arrangement hydraulic cylinders out of operation simultaneously and the emergency disconnection of the drilling riser. Simulating results show that: in normal drilling operation mode, the neutral position tension of the riser tensioner system, compensation accuracy and the gas pressure fluctuation of the accumulator achieve the design goal and meet the standards requirements. Once the failure of two cylinders occurred, enough tension of the system can be maintained by increasing the neutral position pressure. After the emergency disconnection of the riser, the stroke of the tension is less than the maximum design value, and there was no collision between the piston and the cylinder end stop throughout the heaving period. The gas pressure of the accumulator can maintain fairly steady fluctuations. The simulation results are of great significance for development and manufacturing of the hydraulic cylinder direct acting riser tensioner system.