The invention relates to a large size gallium oxide single crystal Czochralski growing method under the normal pressure. The method includes 1, drying gallium oxide powder in vacuo, removing the adsorbed water, pressing to form material blocks, and obtaining gallium oxide blanks; 2, selecting gallium oxide seeds < 010> < 100> or < 001& gt; orientating the seeds, cutting, cleaning through ultrasonic and drying; filling a crucible of a crystal growth furnace with the gallium oxide blanks, evacuating till (1-3) * 10-4Pa, and injecting 1% oxygen and 99% carbon dioxide gas of one atmospheric pressure; heating and melting the gallium oxide blanks by the medium frequency induction heating manner, necking, shouldering, performing constant diameter growth, ending, extracting crystal, and obtaining the large size gallium oxide single crystal. The method adopts mixed gas with proper ratio, an after heater adaptive to the crucible and a heat insulation system, crystal beta-Ga2O3 can grow in a sealed system under the normal pressure, and volatilization and decomposition of the gallium oxide during the growth of the crystal are overcome.