Abstract: Hastelloy-X alloy (as-diposited state) was prepared by selective laser melting, and was treated by thermal isostatic pressure and heat treatments in sequence. The microstructure and tensile properties at room temperature of the alloy after different treatment were investigated. The results show that defects of pores and un-melting powder and sub-structures of melting pool boundaries and dendrites were formed in as-deposited Hastelloy-X alloy at linear energy of 98 J·m^-1; with the increase of linear energy, the relative density of the alloy increased and defects amount decreased. After thermal isostatic pressure treatment, the microstructure consisted of equiaxial grains and network carbides. After thermal isostatic pressure and heat treatment, a part of network carbides dissolved and distributed evenly, and the fine second phases precipitated in grains. The fracture mode of as-deposited alloy was brittle fracture. After thermal isostatic pressure treatment, the plasticity of the alloy was improved and the fracture presented a mixed morphology with secondary cracks and dimples. After thermal isostatic pressure and heat treatment, the plasticity was further improved, the room-temperature tensile properties was better than the standard index of forging parts, and the fracture presented the ductile fracture morphology with the dimple center of fractured carbides.