Selective laser melting (SLM) is a typical rapid forming technique, and complex metallic components with high performance are fabricated directly by using high energy laser beam for melting the metallic powder and layer- by- layer deposition. To investigate the properties of porous aluminum alloy fabricated by SLM, surface morphology, porosity, microstructure, phase composition and micro-mechanical properties of porous aluminum alloy are studied by the scanning electron microscope, energy dispersive X-ray spectroscopy and nanoindentation. The results show that the porosity of the porous aluminum alloy reaches its maximum, the microstructure is refined and the grain size reaches the nanometer level when the laser power is 130 W. The nano hardness of the porous aluminum alloy changes with laser power, while the the elastic modulus does not change obviously. The elastic modulus of the α-Al phase is around 65 GPa, and the elastic modulus of the α-Al+Si phase is around 85 GPa.