The surface spike microstructures are fabricated by irradiating the surface of mono-crystal silicon with femtosecond laser in the atmosphere of SF6 and then coated with aluminium-doped zinc oxide (AZO) thin film by magnetron sputter method. The surface microstructures and optical absorption of coated and uncoated sample are observed and studied. The results indicate that laser energy density has effect on the size and spacing of the spikes on the surface. The main reason for microstructured silicon exhibiting good optical absorption in the wavelength region of 200~1000 nm is multiple-reflection of incident light between the spikes. The rough surface of microstructured silicon and anti-reflection effect of AZO thin film enhance the visible light (400~800 nm) absorption of coated sample and high infrared light reflection of AZO thin film causes a red-shift of reflection peak.