In order to reduce the production cost of copper alloy 3D printing, we use the Cu-10Sn alloy powder prepared by water atomization as raw material for laser selective melting (SLM) experiment, in order to obtain an almost completely dense Cu-10Sn alloy bulk sample by optimizing the SLM processing parameters. The relative density of the sample could be reached to 99.7%. The sample consists of two phases of intermetallic compound Cu41Sn11 and α-Cu solid solution. The grain morphology is mainly the columnar dendrite and interdendritic phases formed along the solidification direction, and high density dislocations are distributed within the crystals. Under the quasi-static tensile condition, the yield strength of the specimen is (392±6) MPa, the tensile strength is (749±5) MPa, and the plastic deformation is 29%±2.3%. The comprehensive mechanical properties are much higher than those of Cu-10Sn alloys prepared by casting methods.