The invention provides an 1100-H24 aluminum alloy plate strip used for a car door and a preparation method thereof. The preparation method comprises the following steps of casting, sawing, milling, homogenization heat treatment, hot rolling, blank annealing, cold rolling, cleaning and finished product annealing. The aluminum alloy plate strip comprises, by mass, 0.35-0.40% of Si, 0.45- 0.50% of Fe, 0.15- 0.20% of Cu, less than 0.05% of Mn, less than 0.05% of Mg, less than 0.05% of Cr, less than 0.05% of Zn, 0.02-0.025% of Ti, and the balance aluminum. According to the production method, the good stability of the mechanical property of the 1100-H24 aluminum alloy plate strip used for the car door can be ensured, the processing formability of the 1100-H24 aluminum alloy plate strip is also greatly improved in the punching process, the rate of finished products is high, and the production efficiency is greatly improved.