Abstract: The optimum design of hydraulic driving control rod is performed in order to improve economics of 200 MW heating reactor. In the new plan, hydraulic control rod drive is arranged above the reactor core and the control rod is moved with the pistons. The advantage of this design is to reduce the ratio of water to uranium and neutron absorption, increase diameter and thickness of cylinder and improve the reliability of control rod. The time of dropping rod was analysed by numerical simulation.