As a media aluminum oxide (Al2O3) thin films deposited by radio frequency plasma-assisted atomic layer deposition (RF-PA-ALD) method were employed to explore the magnetic field effect. Different from normal plasma-assisted ALD (PA-ALD) technology a magnetic field was applied during the whole deposition process. With this novel ALD technology it obtains that the deposition rate in each cycle of ALD is significantly improved. Moreover an ultra-flatness surface, roughness in 0.06 root mass square, was formed in this novel ALD technology. Based on in-situ diagnostic we assume a new mode for Al2O3 growth in the magnetized plasma assisted ALD.