The formation of bubbles generated in a bubble column with 190 mm I.D.from large orifices at high gas velocity was studied for air-deionized water system.The experiments were made with orifice diameters varying from 4 mm to 21 mm and hole gas velocity in the range of 0.8—154.8 m·s-1.The bubble shape and bubble size were recorded by CCD camera，critical hole gas velocity for bubble deformation was derived from the transition of aspect ratio of bubbles.The results showed that bubbles were spherical when hole gas velocity was lower than 20 m·s-1.When hole gas velocity was higher than 50 m·s-1，the shape of bubbles changed to elliptical.A correlation equation was established for bubble size as a function of hole gas velocity and orifice diameter，and the equation predicted the bubble size well for orifice diameter larger than 3 mm and hole gas velocity from 10 m·s-1 to 80 m·s-1 in air-deionized water system.