In conventional liquid engine systems, a gas pressurization system or a turbo pump pressurization system is applied to pressurize oxidant and fuel. In these systems, a large tank to store the pressurization gas or a heavy turbo pump is required. In flight systems where weight saving is required, this heavy pressurization system becomes a severe restriction to the design of whole engine systems. In order to break this situation, a new pressurization system using CO2 has been developed by Japan Aerospace Exploration Agency (JAXA). This system is a type of gas pressurization system, however, the pressurization source CO2 is stored in its liquid phase. Compared to conventional pressurization systems, this can reduce the weight of the tank storing the pressurization source due to the smaller volume of the liquid. During engine burning, LCO2 is vaporized by a regenerative cooling strategy and GCO2 pressurize the oxidant and the fuel. In order to control the pressure, this system has an instrument called charger. This is a type of piston that can control the supply of CO2. A closed-loop line in the system allows the piton to be driven by CO2 itself. This paper shows some results obtained from demonstration experiments conducted in Kakuda, Japan in 2014. These demonstration experiments show a feasibility of this new pressurization system. In the future, this system will be applied to a N2O/Ethanol liquid rocket engine which is now being developed in JAXA.