To study the effects of process parameters on the microstructure and mechanical properties of AlSi10Mg samples during selective laser melting (SLM), different laser powers are adopted to form AlSi10Mg samples. Scanning electron microscopy, X-ray diffraction, tensile testing, nano-indentation testing were used to characterize the melting tracks, forming defects, phase composition, microstructure, mechanical properties, and fracture morphologies of AlSi10Mg samples. Results show that the relative density reaches a maximum value of 99.3% at 350 W, as well as the minimum void defects, the optimum overlap of melting tracks, and the finest gains in the fine grained region. The above sample obtained at 350 W has best mechanical properties, namely, the micro-hardness is 2.338 GPa, the tensile strength is 371.9 MPa and the elongation is 12.67%.