The modulation of the rocket thrust is required for many practical applications regarding certain missions to be performed by the missile. An existing thrust controller with two modes of operation has been studied and analyzed. To upgrade the controller to acquire a continuous gradual thrust modulation, an Electro-Hydraulic Servo-Pressure Controller (EHSPC) has been integrated with the system after making necessary adaptation of the current design. The valve parameters: controlled pressure, input pressure, pilot pressure variations, and input controlling current have been investigated and compared for the two systems using MATLAB SIMULINK program. It was possible to acquire a new system capable of performing a continuous thrust modulation while keeping the other characteristics of the system before modification. KEY WORDSLiquid Propellant Rocket Engine, Thrust Controller, Electro-Hydraulic Servo-valve, and Thrust Modulation.