Selective laser melting（SLM） was adopted to form 17-4 PH high strength steel. The effects of laser power and scanning intervals on the microstructure and properties of the specimens were investigated to determine optimum technological parameters. The microstructure

tensile properties and fracture mechanism of the optimized specimens were analyzed. The results indicate that the low energy density of the laser leads to the unfused region due to the low energy absorption energy when the laser power is 165 W. When the laser power is increased to 205 W

the absorbed energy of the powder is increased

resulting in the spheroidization and increased porosity. The scanning interval has a poorer effect on pore defects than scanning power. When the laser power is 185 W and scanning spacing is 110 μm

the porosity distribution is reduced and the hardness value reaches 370 HV. The microstructure of 17-4 PH high strength steel prepared by SLM is mainly composed of martensite and austenite with precipitation hardening phase of ε-Cu

which improves the hardness of the material. The shape of fracture dimples of tensile specimens is similar with small size

providing higher strength and good toughness.