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In this paper, a novel design approach for a hydro mechanical actuator of LPE control system is investigated. In point of admissible response rate, actuator mechanism is designed rotational. Pay special attention to the control element profile in the design of the actuator. This profile determines the conversion efficiency of the liquid propellant engine. Fitness of engine+ servomotor+ hydro mechanical actuator model to the open loop reference model is the key idea that considered as optimized design basis. Reference model would be determined based on desired dynamic behavior criteria's. With the availability of LPE mathematical model and after the design of hydro mechanical actuator, its parametric model is developed. When engine+ servomotor modeling development are completed and optimization criteria is assigned, parametric model optimization based on evaluation algorithm would be accomplished. Finally, fitness improvement between integrated and open loop reference models is evaluated. Before starting the optimized design process, the input signal and its corresponding cost function properly defined. Results shown by correction of actuator geometrical parameters and compensator gain, cost function amount – based on tracking error of liquid propellant engine combustion chamber pressure reference signal - 4 times is improved.