Aluminium (Al) thin films are prepared on the quartz substrate, and meanwhile Al nanoparticles are obtained by baking the Al thin films. The absorption property of Al nanoparticles with different thicknesses are studied. The results show that the roughness of Al thin films increases with the increase of baking temperature. When the baking temperature reaches 300 ℃, the Al thin films are completely transformed into Al nanoparticles. When the film thickness varies from 5 nm to 25 nm, the redshift of the thin film resonance absorption peak is 40 nm at the baking temperature of 300 ℃. This fabrication process of Al nanoparticles is simple, time-saving, low-cost, and high-efficiency.