The invention belongs to the field of preparation of aluminum and aluminum alloy strips, and in particular, relates to an aluminum alloy strip for anodic oxidation and a preparation method thereof. The aluminum alloy strip comprises the following components: 0.15-0.25 wt% of Cr, 2.5-3.5 wt% of Mg, Si not more than 0.08 wt%, Fe not more than 0.15 wt%, Fe/Si of 1-3, Cu not more than 0.05 wt%, Mn not more than 0.05 wt%, Ti not more than 0.05 wt%, and the balance of aluminum. After batching, an aluminum alloy plate strip for an anode with a yield strength of more than 200 MPa and highlighted back anode is prepared through a cold rolling process; and the strip is suitable for serving as an appearance part of such products as electronic and electric appliances, such as mobile phones and computer shells, so that the application of the aluminum alloy strip to the field of electronic devices is widened.