A high pressure sintering method was devised to fabricate high density and strength BaZr0.9Y0.1O3-delta (BZY) ceramic at 0.6 GPa and 1100 degrees C for the first time. The mechanical properties and electrochemical response of the ceramic in high pressure hydrothermal fluids were tested in a self-designed autoclave. Results shows that the ceramic can be processed into fixed shape, it remains stable and a rapid electrochemical response was observed after exposing to water vapor at 340 degrees C and 14 MPa for 20 h, which makes the product an excellent candidate electrolyte material for in-situ measurement of H-2 in high pressure hydrothermal fluids.