To solve the problem of laser surface processing not forming high-chromatic-aberration and high-contrast black patterns on aluminum alloys, a fiber laser machine with a 4-ns pulse width is used to mark 5052 anodic aluminum oxide (AAO) alloy at a scanning speed of 130 mm/s, a frequency of 300 kHz, a scanning pitch of 0.005 mm, and a setup power of 27%P0-33%P0 (P0 is the rated power of the laser). We obtain a black pattern with a high chromatic aberration and high contrast. The effect of the laser power on the contrast and micro-morphology of the pattern is studied, and the mechanism of pattern formation by laser surface processing on the AAO is analyzed. Results show that when the laser power exceeds 1.64 W, the laser energy reaches the melting threshold of aluminum and a pattern is formed on the surface. With the increase of laser power, the contrast gradually increases. When the laser power increases to 2.13-2.76 W, the AAO surface forms a fine-crack micro-morphology by melting and evaporation, the macroscopic display is black, and the contrast reaches the maximum. When the laser power increases to 3.32 W, the surface of the aluminum material melts completely, the fine-crack micro-morphology disappears, the macroscopic display is grayish white, and the contrast decreases. These results contribute to further research on the mechanism of laser surface processing on aluminum, which is helpful for promoting the development of the Internet of Things.