The surface microstructured silicon prepared by femtosecond laser pulses irradiation in SF6 shows significantly enhanced light absorption over a wide wavelength range. Absorptance of microstructured silicon is measured from 2 to 16μm, and the absorptance can up to 0.8 in the measured wavelength range. The absorptance of microstructured silicon increases as the height of spikes increases. Emissivity of microstructured silicon at different temperatures(100°C-400°C) is measured from 2.5μm to 25μm. Greatly enhanced emissivity compared to that of flat silicon was observed. At a certain temperature, with increasing the height of the spikes, the emissivity increases. For a sample with 13–14μm high spikes, the emissivity at a temperature of 100°C is approximately 0.96. A tentative explanation for the high absorptance of microstructured silicon has been carried out from three aspects: impurity states, structure defects and multiple reflection of light between spikes. The excellent properties of microstructured silicon make it a promising candidate for applications of infrared detectors, silicon solar cells, flat blackbody source and so on.