The fly ash was activated by high enery ball milling, and the ball gradation, ball/powder weight ratio, rotate speed and milling time were treated by orthogonal experiment. The Al2O3 was obtained by calcined with a percentage of fly ash activated with different time and Na2CO3. The effect of surface mechanical activation on extraction rate of Al2O3 was tested and analyzed, and finally the most optimized parameter and the kinetics of the extraction processes were found out. The results show that, the extraction of Al2O3 reached 91.15% when the surface mechanical activation time is 6 h with L/S = 6, and the acid concentration 4 mol/L at the leaching temperature 90℃. The reaction can be described by shrinking core model and the activation energy is 60.87 kJ/mol while the reaction order is 0.1701.