Disclosed is a method of preparing single crystal ingot of barium zirconium oxide. The method includes preparing a cylindrical BaZrO3 ceramic by pulverizing a BaZrO3 compound into a powder and sintering the same into a cylindrical ceramic form, ii) fixing two cylindrical BaZrO3 ceramics to an optical floating zone furnace, joining the two cylindrical BaZrO3 ceramics together and melting the junction at a temperature of 2,600 to 3,500° C. using light emitted from a xenon lamp or laser, and after the melting, moving the two cylindrical BaZrO3 ceramics in a direction parallel to an axis of rotation thereof, enabling the molten junction to be solidified, and thereby growing a single crystal.