The present work provides a simple and effective route for the production of high quality CaZr0.9In0.1O3-delta (CZI) at relatively low temperature by using high-pressure sintering method. A comparison of structure and conductivity between pressureless sintered CZI (PL-CZI) and high-pressure sintered CZI (HP-CZI) ceramics was carried out using X-ray diffraction as well as scanning electron microscope and AC impedance spectroscopy. In addition, the electrochemical response and sealing performance of the CZI ceramics in high-pressure hydrothermal fluids were tested in a self-designed autoclave. The introduction of pressure during sintering endowed the CZI ceramic with high conductivity, excellent mechanical performance and favorable corrosion resistance; these traits make the HP-CZI ceramic an ideal electrolyte material for hydrogen sensors in high-pressure hydrothermal systems.